radv: use indirect buffer for initial gfx state.

radv: use indirect buffer for initial gfx state.

This puts the common gfx state for the device into an
indirect buffer, and just calls out to it, on CIK and above.

This is taken from what radeonsi does.

Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Signed-off-by: Dave Airlie <airlied@redhat.com>