r600g: fix op3 abs issue

r600g: fix op3 abs issue

This code to handle absolute values on op3 srcs was a bit too simple,
it really needs a temp reg per src, not one per channel, make it
easier and let sb clean up the mess.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89831

Reviewed-by: Glenn Kennard <glenn.kennard@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>