z/Architecture Principles of Operation details LOCR/LOCGR to be RRF-c
format, with the operands printed in the form LOCR/LOCGR R1,R2,M3,
where M3 is binary encoded in bits 16-20.  Current disassembler
is printing the operands in the wrong order, and extracting the Mask
from the wrong bits.

R=jyan@ca.ibm.com, michael_dawson@ca.ibm.com

Change-Id: I30baaab16ab3dbf879df381cd1f0978a66a214a6
Reviewed-on: https://chromium-review.googlesource.com/1091139Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Joran Siu <joransiu@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#53593}