[arch][arm-m] wfi in the idle loop
[arch][arm-m] wfi in the idle loop

pablomarx/lk,GCrean/lk,littlekernel/lk,littlekernel/lk,ianloic/lk,sndnvaps/lk,srodrig1/lk,minglun-tsai/lk,M1cha/lk,travisg/lk,hollanderic/lkstuff,M1cha/lk,skabet/lk,sndnvaps/lk,pablomarx/lk,skabet/lk,ianloic/lk,littlekernel/lk,GCrean/lk,ErikCorryGoogle/lk,littlekernel/lk,M1cha/lk,hollanderic/lkstuff,sndnvaps/lk,pablomarx/lk,grub4android/lk,nvll/lk,travisg/lk,srodrig1/lk,hollanderic/lkstuff,GCrean/lk,M1cha/lk,nvll/lk,grub4android/lk,GCrean/lk,sndnvaps/lk,minglun-tsai/lk,ErikCorryGoogle/lk,M1cha/lk,nvll/lk,srodrig1/lk,minglun-tsai/lk,pablomarx/lk,skabet/lk,ianloic/lk,travisg/lk,grub4android/lk,skabet/lk,pablomarx/lk,nvll/lk,nvll/lk,ErikCorryGoogle/lk,grub4android/lk,srodrig1/lk,hollanderic/lkstuff,skabet/lk,minglun-tsai/lk,travisg/lk,grub4android/lk,srodrig1/lk,sndnvaps/lk,GCrean/lk,ErikCorryGoogle/lk,ianloic/lk