runtime: remove instruction linked with AIX new stack layout

This instruction was linked with a new stack layout which might be
needed for AIX. This change might not be taken finally. So, this
instruction must be removed.

See https://go-review.googlesource.com/c/go/+/138733

Change-Id: Ic4a2566e2882696b437eb817d980b7c4bfc03b18
Reviewed-on: https://go-review.googlesource.com/c/144957
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/asm_ppc64x.s

@@ -519,9 +519,6 @@ again:
 // the BL deferreturn and jmpdefer rewinds to that.
 TEXT runtime·jmpdefer(SB), NOSPLIT|NOFRAME, $0-16
 	MOVD	0(R1), R31
-#ifdef GOOS_aix
-	MOVD	16(R31), R31	// caller LR is on the previous stack frame on AIX
-#endif
 	SUB     $8, R31
 	MOVD	R31, LR