spi: implemented write functions
spi: implemented write functions

Still basic, more work needed

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

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