bytes: fix typo in ppc64le asm for Compare

Correcting a line in asm_ppc64x.s in the cmpbodyLE function
that originally was R14 but accidentally changed to R4.

Fixes golang#17488

Change-Id: Id4ca6fb2e0cd81251557a0627e17b5e734c39e01
Reviewed-on: https://go-review.googlesource.com/31266
Reviewed-by: Michael Munday <munday@ca.ibm.com>
Run-TryBot: Michael Munday <munday@ca.ibm.com>

src/runtime/asm_ppc64x.s

@@ -853,7 +853,7 @@ loop32a:
 	BNE	cmpne		// further compare for LT or GT
 	MOVD	16(R5),R9	// get next pair of doublewords
 	MOVD	16(R6),R10
-	CMPU	R4,R15		// bytes match?
+	CMPU	R14,R15		// bytes match?
 	MOVD	$8,R16		// set up for cmpne
 	BNE	cmpne		// further compare for LT or GT
 	MOVD	24(R5),R14	// get next pair of doublewords