[arch][arm-m] move the initial stack over to the .prebss. section
[arch][arm-m] move the initial stack over to the .prebss. section

The explicit initial stack section was unnecessary, since there was
already a more generic .bss.prebss. mechanism in the linker script.

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