gallium: add CAPs to support HW atomic counters. (v3)

gallium: add CAPs to support HW atomic counters. (v3)

This looks like an evergreen specific feature, but with atomic
counters AMD have hw specific counters they use instead of operating
on buffers directly. These are separate to the buffer atomics,
so require different limits and code paths.

I've left the CAP for atomic type extensible in case someone
else has a variant on this sort of thing (freedreno maybe?)
and needs to change it.

This adds all the CAPs required to add support for those atomic
counters, along with a related CAP for limiting the number of
output resources.

I'd like to land this and the st patch then I can start to
upstream the evergreen support for these and other GL4.x features.

v2: drop the ATOMIC_COUNTER_MODE cap, just use the return
from the HW counters. If 0 we use the current mode.
v3: fix some rebase errors (Gert Wollny)

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Tested-By: Gert Wollny <gw.fossdev@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>