[RT-ARM] Syntax unified for aeabi_mem* functions

Use unified syntax for builtins/arm/aeabi_mem*.S.

This makes these files consistent with the others.

This fixes a problem on the linker, which can fail with the message
"relocation truncated to fit: R_ARM_THM_JUMP11 against symbol"

Patch by Kor Nielsen.

llvm-svn: 275264