mraa.c: subplatforms need to be defined after platforms
mraa.c: subplatforms need to be defined after platforms

This also means arm subplatforms can work and removes a plat == NULL check
which will never be true if -DUSBPLAT=ON

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

jontrulson/mraa,mircea/mraa,alext-mkrs/mraa,KurtE/mraa,Propanu/mraa,Pillar1989/mraa,malikabhi05/mraa,intel-iot-devkit/mraa,Pillar1989/mraa,ProfFan/mraa,tripzero/mraa,anonymouse64/mraa,damcclos/mraa,stefan-andritoiu/mraa,whbruce/mraa,arunlee77/mraa,yoyojacky/mraa,jontrulson/mraa,KurtE/mraa,mircea/mraa,tripzero/mraa,Kiritoalex/mraa,arfoll/mraa,jontrulson/mraa,g-vidal/mraa,smileboywtu/mraa,Kiritoalex/mraa,ProfFan/mraa,yongli3/mraa,Hbrinj/mraa,alext-mkrs/mraa,Jon-ICS/mraa,jontrulson/mraa,jontrulson/mraa,sergev/mraa,Jon-ICS/mraa,spitfire88/mraa,arunlee77/mraa,stefan-andritoiu/mraa-gpio-chardev,KurtE/mraa,damcclos/mraa,nioinnovation/mraa,KurtE/mraa,spitfire88/mraa,petreeftime/mraa,Pillar1989/mraa,yongli3/mraa,nioinnovation/mraa,stefan-andritoiu/mraa-gpio-chardev,Jon-ICS/mraa,stefan-andritoiu/mraa-gpio-chardev,neuroidss/mraa,petreeftime/mraa,arfoll/mraa,tripzero/mraa,sergev/mraa,matt-auld/mraa,sergev/mraa,KurtE/mraa,g-vidal/mraa,malikabhi05/mraa,malikabhi05/mraa,Propanu/mraa,alext-mkrs/mraa,g-vidal/mraa,yongli3/mraa,ncrastanaren/mraa,ncrastanaren/mraa,stefan-andritoiu/mraa,w4ilun/mraa,allela-roy/mraa,andreivasiliu2211/mraa,Hbrinj/mraa,petreeftime/mraa,Hbrinj/mraa,arfoll/mraa,matt-auld/mraa,stefan-andritoiu/mraa,sergev/mraa,smileboywtu/mraa,arfoll/mraa,ncrastanaren/mraa,Propanu/mraa,ncrastanaren/mraa,spitfire88/mraa,stefan-andritoiu/mraa,alex1818/mraa,stefan-andritoiu/mraa-gpio-chardev,whbruce/mraa,damcclos/mraa,neuroidss/mraa,allela-roy/mraa,nioinnovation/mraa,w4ilun/mraa,intel-iot-devkit/mraa,alext-mkrs/mraa,Propanu/mraa,stefan-andritoiu/mraa-gpio-chardev,smileboywtu/mraa,stefan-andritoiu/mraa,intel-iot-devkit/mraa,whbruce/mraa,neuroidss/mraa,arunlee77/mraa,whbruce/mraa,anonymouse64/mraa,g-vidal/mraa,anonymouse64/mraa,petreeftime/mraa,alex1818/mraa,intel-iot-devkit/mraa,arunlee77/mraa,alex1818/mraa,yoyojacky/mraa,ncrastanaren/mraa,intel-iot-devkit/mraa,andreivasiliu2211/mraa,yongli3/mraa,allela-roy/mraa,spitfire88/mraa,matt-auld/mraa,andreivasiliu2211/mraa,w4ilun/mraa,sergev/mraa,alext-mkrs/mraa,w4ilun/mraa,mircea/mraa,malikabhi05/mraa,Kiritoalex/mraa,Hbrinj/mraa,ProfFan/mraa,g-vidal/mraa,andreivasiliu2211/mraa,ProfFan/mraa,arfoll/mraa,Propanu/mraa,yoyojacky/mraa,malikabhi05/mraa,yongli3/mraa