ir3: Set up full/half register conflicts correctly

ir3: Set up full/half register conflicts correctly

Setting up transitive conflicts between a full register and its two
half registers (eg r0.x and hr0.x and hr0.y) will make the half
registers conflict.  They don't actually conflict and this prevents us
from using both at the same time.

Add and use a new ra helper that sets up transitive conflicts between
a register and its subregisters, except it carefully avoids the
subregister conflict.

Signed-off-by: Kristian H. Kristensen <hoegsberg@google.com>
Reviewed-by: Rob Clark <robdclark@chromium.org>