This patch fixes the msa copy_[s|u]_df instruction emulation when
the destination register rd is zero. Without this patch the zero
register would get clobbered, which should never happen because it
is supposed to be hardwired to 0.

Fix this corner case by explicitly checking rd = 0 and effectively
making these instructions emulation no-op in that case.
Signed-off-by: NMiodrag Dinic <miodrag.dinic@imgtec.com>
Reviewed-by: NAurelien Jarno <aurelien@aurel32.net>
Acked-by: NAurelien Jarno <aurelien@aurel32.net>
Signed-off-by: NYongbok Kim <yongbok.kim@imgtec.com>