galileo gen2: add uart definitions
galileo gen2: add uart definitions

Also added hook for setting output buffers.
fixes #36

Signed-off-by: Thomas Ingleby <cea8b9d820e871fd22532c955ca84ff867a004a3@intel.com>

jontrulson/mraa,arfoll/mraa,damcclos/mraa,neuroidss/mraa,timrtoo/Intel,ProfFan/mraa,sergev/mraa,stefan-andritoiu/mraa-gpio-chardev,stefan-andritoiu/mraa-gpio-chardev,timrtoo/Intel,whbruce/mraa,spitfire88/mraa,ncrastanaren/mraa,KurtE/mraa,nioinnovation/mraa,intel-iot-devkit/mraa,g-vidal/mraa,Meirtz/mraa,sundw2014/mraa,arunlee77/mraa,intel-iot-devkit/mraa,nioinnovation/mraa,SyrianSpock/mraa,jontrulson/mraa,damcclos/mraa,Meirtz/mraa,tripzero/mraa,petreeftime/mraa,anonymouse64/mraa,stefan-andritoiu/mraa,seem-sky/mraa,KurtE/mraa,jontrulson/mraa,w4ilun/mraa,Propanu/mraa,Kiritoalex/mraa,Pillar1989/mraa,timrtoo/Intel,sergev/mraa,KurtE/mraa,g-vidal/mraa,stefan-andritoiu/mraa,KurtE/mraa,neuberfran/mraa,jontrulson/mraa,Propanu/mraa,g-vidal/mraa,andreivasiliu2211/mraa,andreivasiliu2211/mraa,STANAPO/mraa,yongli3/mraa,allela-roy/mraa,alexandru-elisei/mraa,malikabhi05/mraa,jontrulson/mraa,seem-sky/mraa,yoyojacky/mraa,g-vidal/mraa,tripzero/mraa,timrtoo/Intel,yangjae/mraa,yangjae/mraa,sundw2014/mraa,Kiritoalex/mraa,neuberfran/mraa,zBMNForks/mraa,arfoll/mraa,alexandru-elisei/mraa,petreeftime/mraa,stefan-andritoiu/mraa,ncrastanaren/mraa,ProfFan/mraa,STANAPO/mraa,noahchense/mraa,SyrianSpock/mraa,sundw2014/mraa,arfoll/mraa,STANAPO/mraa,Propanu/mraa,pctj101/mraa,neuroidss/mraa,w4ilun/mraa,alext-mkrs/mraa,seem-sky/mraa,alext-mkrs/mraa,whbruce/mraa,Jon-ICS/mraa,petreeftime/mraa,alexandru-elisei/mraa,nioinnovation/mraa,matt-auld/mraa,ncrastanaren/mraa,neuberfran/mraa,mircea/mraa,yongli3/mraa,anonymouse64/mraa,yongli3/mraa,SyrianSpock/mraa,yoyojacky/mraa,whbruce/mraa,noahchense/mraa,malikabhi05/mraa,Propanu/mraa,yoyojacky/mraa,seem-sky/mraa,zBMNForks/mraa,ProfFan/mraa,stefan-andritoiu/mraa,Kiritoalex/mraa,Hbrinj/mraa,neuroidss/mraa,smileboywtu/mraa,sergev/mraa,andreivasiliu2211/mraa,stefan-andritoiu/mraa-gpio-chardev,allela-roy/mraa,noahchense/mraa,yongli3/mraa,g-vidal/mraa,mircea/mraa,spitfire88/mraa,intel-iot-devkit/mraa,Pillar1989/mraa,ncrastanaren/mraa,Pillar1989/mraa,arunlee77/mraa,yangjae/mraa,matt-auld/mraa,KurtE/mraa,malikabhi05/mraa,matt-auld/mraa,sergev/mraa,pctj101/mraa,alex1818/mraa,whbruce/mraa,pctj101/mraa,andreivasiliu2211/mraa,alex1818/mraa,yangjae/mraa,alext-mkrs/mraa,sergev/mraa,smileboywtu/mraa,neuberfran/mraa,arunlee77/mraa,petreeftime/mraa,alex1818/mraa,zBMNForks/mraa,alexandru-elisei/mraa,allela-roy/mraa,stefan-andritoiu/mraa-gpio-chardev,smileboywtu/mraa,Hbrinj/mraa,intel-iot-devkit/mraa,Jon-ICS/mraa,spitfire88/mraa,pctj101/mraa,w4ilun/mraa,damcclos/mraa,sundw2014/mraa,Hbrinj/mraa,anonymouse64/mraa,stefan-andritoiu/mraa,arfoll/mraa,malikabhi05/mraa,arunlee77/mraa,alext-mkrs/mraa,noahchense/mraa,sundw2014/mraa,Jon-ICS/mraa,Meirtz/mraa,alexandru-elisei/mraa,noahchense/mraa,malikabhi05/mraa,arfoll/mraa,Hbrinj/mraa,intel-iot-devkit/mraa,ProfFan/mraa,tripzero/mraa,stefan-andritoiu/mraa-gpio-chardev,w4ilun/mraa,mircea/mraa,ncrastanaren/mraa,timrtoo/Intel,spitfire88/mraa,yongli3/mraa,pctj101/mraa,alext-mkrs/mraa,Propanu/mraa,seem-sky/mraa,neuberfran/mraa