Revert "[release-branch.go1.5] runtime: check that stack barrier unwind is in sync"

This reverts commit f265044a.

Change-Id: I454f9da3a40d6724ab106aae904b8e77756aae99
Reviewed-on: https://go-review.googlesource.com/14383
Run-TryBot: Chris Broadfoot <cbro@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/asm_amd64.s

@@ -346,12 +346,7 @@ TEXT runtime·stackBarrier(SB),NOSPLIT,$0
 	MOVQ	(g_stkbar+slice_array)(CX), DX
 	MOVQ	g_stkbarPos(CX), BX
 	IMULQ	$stkbar__size, BX	// Too big for SIB.
-	MOVQ	stkbar_savedLRPtr(DX)(BX*1), R8
 	MOVQ	stkbar_savedLRVal(DX)(BX*1), BX
-	// Assert that we're popping the right saved LR.
-	CMPQ	R8, SP
-	JNE	2(PC)
-	MOVL	$0, 0
 	// Record that this stack barrier was hit.
 	ADDQ	$1, g_stkbarPos(CX)
 	// Jump to the original return PC.