Add HAS_HW_DIV to control the compilation of __udivsi3.

libgcc.a will contain __udivsi3 if -mcpu=cortex-a15 is specified.

Bug: 7961327

cherry-picked from internal master.

Change-Id: Ia00295cee23f1af3dacff4fcdf612b312897327c

Conflicts:
	runtime/lib/divsi3.c
fix no endif derp

Change-Id: I7a46787bb047764f64bda97282ab9e1ebdde016c