gpio.c: add pin number to export fail message
gpio.c: add pin number to export fail message

Signed-off-by: Brendan Le Foll <3e0e8c4069934e8b47d99704927a85c66c0ceb33@intel.com>

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