On ARM, STREX does not permit the same register used as both the
source and the destination. Reject the bad instruction.

The assembler also accepted special cases
	STREX R0, (R1)	as STREX R0, (R1), R0
	STREX (R1), R0	as STREX R0, (R1), R0
both are illegal. Remove this special case as well.

For STREXD, check that the destination is not source, and not
source+1. Also check that the source register is even numbered,
as required by the architecture's manual.

Fixes #22268.

Change-Id: I6bfde86ae692d8f1d35bd0bd7aac0f8a11ce8e22
Reviewed-on: https://go-review.googlesource.com/71190
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>