The current implementation of l*arx instructions does not accept non-zero
offsets in RA nor the EH field. This change adds full functionality to those
instructions.

Updates #23845

Change-Id: If113f70d11de5f35f8389520b049390dbc40e863
Reviewed-on: https://go-review.googlesource.com/99635
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>