When RS and RA are both used as operands by an instruction,
RS takes precedence over RA. In such cases, either both the
register operands are used as sources or RS is a source and
RA is a destination.
This changes the order by giving RS the highest precedence
and will be useful for proper disassembly generation.
Change-Id: If351a03a814653f2f371afa936ec7a5cd4377b3a Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>