builtins: correct __umodsi3, __udivsi3 on ARM

When building the builtins for a modern CPU (idiv support), __umodsi3 was
completely incorrect as it would behave as __udivmosi3, which takes a tertiary
parameter which is a pointer.

__udivsi3 was also incorrect, returning the remainder in r1.  Although this
would not result in any crash or invalid behaviour as r1 is a caller saved
register in AAPCS, this is unnecessary.  Simply perform the division ignoring
the remainder.

llvm-svn: 215295
diff --git a/compiler-rt/lib/builtins/arm/udivsi3.S b/compiler-rt/lib/builtins/arm/udivsi3.S
index bb5f8a0..34bd713 100644
--- a/compiler-rt/lib/builtins/arm/udivsi3.S
+++ b/compiler-rt/lib/builtins/arm/udivsi3.S
@@ -27,9 +27,7 @@
 #if __ARM_ARCH_EXT_IDIV__
 	tst     r1, r1
 	beq     LOCAL_LABEL(divby0)
-	mov 	r3, r0
-	udiv	r0, r3, r1
-	mls 	r1, r0, r1, r3
+	udiv	r0, r0, r1
 	bx  	lr
 #else
 	cmp	r1, #1