Fold offsets for:

  {ADD,SUB,MUL}[SD]mem
  ADD[LQ]constmem
  {ADD,SUB,AND,OR,XOR}[LQ]mem

Cumulatively, the rules trigger ~900 times in all.bash.

Fixes #23325

Change-Id: If6c701f68fa0b57907a353a07a516b914127d0d8
Reviewed-on: https://go-review.googlesource.com/98035
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>