pan/bi: Add bifrost_reg_mode enum

This generalizes the previous control field, adding in the full set of
enums required for 16-bit writemasks.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6793>
1 file changed