The arm assembler incorrectly encodes the following instructions.
"MUL R2, R4" -> 0xe0040492 ("MUL R4, R2, R4")
"MUL R2, R4, R4" -> 0xe0040492 ("MUL R4, R2, R4")

The CL fixes that issue.

fixes #25347

Change-Id: I883716c7bc51c5f64837ae7d81342f94540a58cb
Reviewed-on: https://go-review.googlesource.com/112737Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>