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

Fixes #17488

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