freedreno/a6xx: separate rast stateobj for prim restart

freedreno/a6xx: separate rast stateobj for prim restart

This lets us move PC_PRIMITIVE_CNTL into the rasterizr stateobj, rather
than unconditionally emitting it directly in the cmdstream on every
draw.

This also starts adding some tracking about previous draw state, so that
following patches can limit some of the register writes we currently
emit on every draw.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3435>