internals.md: Add doc to explain pwm internally is all in us
internals.md: Add doc to explain pwm internally is all in us

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

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