packet_data_generator: update of_protocol upstream
packet_data_generator: update of_protocol upstream

merely a clean up for a pullup request.  no functionality changes.

also, update comments.

Signed-off-by: YAMAMOTO Takashi <458bba2e4a8704776b33478100c98529b639cd9e@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>

OpenState-SDN/ryu,Tesi-Luca-Davide/ryu,o3project/ryu-oe,shinpeimuraoka/ryu,sivaramakrishnansr/ryu,lzppp/mylearning,Tejas-Subramanya/RYU_MEC,shinpeimuraoka/ryu,jkoelker/ryu,fkakuma/ryu,Tesi-Luca-Davide/ryu,evanscottgray/ryu,StephenKing/summerschool-2015-ryu,diogommartins/ryu,torufuru/OFPatchPanel,StephenKing/ryu,gareging/SDN_Framework,shinpeimuraoka/ryu,pichuang/ryu,hisaharu/ryu,fujita/ryu,openvapour/ryu,jalilm/ryu,alyosha1879/ryu,umkcdcrg01/ryu_openflow,sivaramakrishnansr/ryu,torufuru/oolhackathon,zangree/ryu,ttsubo/ryu,osrg/ryu,Tejas-Subramanya/RYU_MEC,yamada-h/ryu,Tejas-Subramanya/RYU_MEC,lagopus/ryu-lagopus-ext,gopchandani/ryu,Tejas-Subramanya/RYU_MEC,darjus-amzn/ryu,ttsubo/ryu,ttsubo/ryu,John-Lin/ryu,openvapour/ryu,pichuang/ryu,diogommartins/ryu,habibiefaried/ryu,jkoelker/ryu,StephenKing/summerschool-2015-ryu,zangree/ryu,darjus-amzn/ryu,TakeshiTseng/ryu,osrg/ryu,torufuru/OFPatchPanel,osrg/ryu,TakeshiTseng/ryu,darjus-amzn/ryu,hisaharu/ryu,muzixing/ryu,shinpeimuraoka/ryu,hisaharu/ryu,OpenState-SDN/ryu,John-Lin/ryu,pichuang/ryu,OpenState-SDN/ryu,yamt/ryu,habibiefaried/ryu,openvapour/ryu,Tesi-Luca-Davide/ryu,alanquillin/ryu,ynkjm/ryu,alyosha1879/ryu,ntts-clo/ryu,OpenState-SDN/ryu,o3project/ryu-oe,sivaramakrishnansr/ryu,fkakuma/ryu,ynkjm/ryu,OpenState-SDN/ryu,evanscottgray/ryu,pichuang/ryu,ysywh/ryu,fkakuma/ryu,gareging/SDN_Framework,takahashiminoru/ryu,StephenKing/summerschool-2015-ryu,elahejalalpour/ELRyu,openvapour/ryu,castroflavio/ryu,diogommartins/ryu,yamt/ryu,StephenKing/summerschool-2015-ryu,Zouyiran/ryu,iwaseyusuke/ryu,ntts-clo/mld-ryu,StephenKing/summerschool-2015-ryu,fujita/ryu,jalilm/ryu,jazzmes/ryu,umkcdcrg01/ryu_openflow,muzixing/ryu,Tejas-Subramanya/RYU_MEC,jalilm/ryu,haniehrajabi/ryu,John-Lin/ryu,elahejalalpour/ELRyu,jkoelker/ryu,fujita/ryu,alanquillin/ryu,elahejalalpour/ELRyu,torufuru/oolhackathon,ysywh/ryu,gopchandani/ryu,lsqtongxin/ryu,lsqtongxin/ryu,umkcdcrg01/ryu_openflow,diogommartins/ryu,Tesi-Luca-Davide/ryu,hisaharu/ryu,ysywh/ryu,zangree/ryu,TakeshiTseng/ryu,Zouyiran/ryu,jazzmes/ryu,hisaharu/ryu,gopchandani/ryu,elahejalalpour/ELRyu,alyosha1879/ryu,ttsubo/ryu,umkcdcrg01/ryu_openflow,lzppp/mylearning,lagopus/ryu-lagopus-ext,elahejalalpour/ELRyu,TakeshiTseng/ryu,ynkjm/ryu,lzppp/mylearning,ysywh/ryu,torufuru/oolhackathon,gareging/SDN_Framework,zangree/ryu,darjus-amzn/ryu,lzppp/mylearning,Zouyiran/ryu,jalilm/ryu,alanquillin/ryu,zyq001/ryu,fkakuma/ryu,yamt/ryu,openvapour/ryu,lagopus/ryu-lagopus-ext,ynkjm/ryu,Tesi-Luca-Davide/ryu,takahashiminoru/ryu,haniehrajabi/ryu,sivaramakrishnansr/ryu,zyq001/ryu,lsqtongxin/ryu,lsqtongxin/ryu,haniehrajabi/ryu,jazzmes/ryu,osrg/ryu,habibiefaried/ryu,fkakuma/ryu,lzppp/mylearning,ynkjm/ryu,fujita/ryu,StephenKing/ryu,gareging/SDN_Framework,muzixing/ryu,Zouyiran/ryu,lagopus/ryu-lagopus-ext,ttsubo/ryu,StephenKing/ryu,ysywh/ryu,ntts-clo/ryu,iwaseyusuke/ryu,osrg/ryu,alanquillin/ryu,zyq001/ryu,muzixing/ryu,alyosha1879/ryu,yamada-h/ryu,haniehrajabi/ryu,shinpeimuraoka/ryu,iwaseyusuke/ryu,haniehrajabi/ryu,alanquillin/ryu,umkcdcrg01/ryu_openflow,gareging/SDN_Framework,gopchandani/ryu,StephenKing/ryu,takahashiminoru/ryu,TakeshiTseng/ryu,zangree/ryu,lagopus/ryu-lagopus-ext,zyq001/ryu,habibiefaried/ryu,fujita/ryu,diogommartins/ryu,StephenKing/ryu,iwaseyusuke/ryu,lsqtongxin/ryu,gopchandani/ryu,sivaramakrishnansr/ryu,takahashiminoru/ryu,mikhaelharswanto/ryu,evanscottgray/ryu,castroflavio/ryu,Zouyiran/ryu,John-Lin/ryu,castroflavio/ryu,ntts-clo/mld-ryu,iwaseyusuke/ryu,yamt/ryu,muzixing/ryu,takahashiminoru/ryu,zyq001/ryu,mikhaelharswanto/ryu,jalilm/ryu,habibiefaried/ryu,yamt/ryu,pichuang/ryu,John-Lin/ryu,darjus-amzn/ryu