mraa-gpio.c: Add return to list_pins
mraa-gpio.c: Add return to list_pins

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

andreivasiliu2211/mraa,sergev/mraa,KurtE/mraa,arunlee77/mraa,spitfire88/mraa,arfoll/mraa,KurtE/mraa,spitfire88/mraa,yongli3/mraa,yongli3/mraa,Propanu/mraa,alext-mkrs/mraa,andreivasiliu2211/mraa,ncrastanaren/mraa,stefan-andritoiu/mraa-gpio-chardev,ProfFan/mraa,ncrastanaren/mraa,Pillar1989/mraa,andreivasiliu2211/mraa,andreivasiliu2211/mraa,Propanu/mraa,stefan-andritoiu/mraa-gpio-chardev,w4ilun/mraa,sergev/mraa,Hbrinj/mraa,sergev/mraa,arunlee77/mraa,stefan-andritoiu/mraa,jontrulson/mraa,malikabhi05/mraa,jontrulson/mraa,jontrulson/mraa,stefan-andritoiu/mraa-gpio-chardev,Pillar1989/mraa,g-vidal/mraa,malikabhi05/mraa,yongli3/mraa,petreeftime/mraa,arfoll/mraa,stefan-andritoiu/mraa,jontrulson/mraa,jontrulson/mraa,arfoll/mraa,g-vidal/mraa,petreeftime/mraa,w4ilun/mraa,g-vidal/mraa,whbruce/mraa,malikabhi05/mraa,petreeftime/mraa,alext-mkrs/mraa,spitfire88/mraa,Jon-ICS/mraa,Hbrinj/mraa,stefan-andritoiu/mraa,Propanu/mraa,whbruce/mraa,malikabhi05/mraa,KurtE/mraa,arunlee77/mraa,Hbrinj/mraa,Propanu/mraa,arfoll/mraa,intel-iot-devkit/mraa,Jon-ICS/mraa,yongli3/mraa,ncrastanaren/mraa,intel-iot-devkit/mraa,stefan-andritoiu/mraa,ProfFan/mraa,whbruce/mraa,arfoll/mraa,intel-iot-devkit/mraa,Jon-ICS/mraa,Pillar1989/mraa,petreeftime/mraa,whbruce/mraa,stefan-andritoiu/mraa,ncrastanaren/mraa,sergev/mraa,sergev/mraa,alext-mkrs/mraa,intel-iot-devkit/mraa,alext-mkrs/mraa,Propanu/mraa,spitfire88/mraa,ProfFan/mraa,yongli3/mraa,arunlee77/mraa,stefan-andritoiu/mraa-gpio-chardev,w4ilun/mraa,alext-mkrs/mraa,ProfFan/mraa,Hbrinj/mraa,ncrastanaren/mraa,g-vidal/mraa,stefan-andritoiu/mraa-gpio-chardev,malikabhi05/mraa,intel-iot-devkit/mraa,g-vidal/mraa,w4ilun/mraa,KurtE/mraa,KurtE/mraa