radv: fix MSAA on SI gpus.

radv: fix MSAA on SI gpus.

This ports the workaround from radeonsi, that was missing in radv.

This fixes Talos rendering when MSAA is enabled on my Tahiti card.

Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Fixes: f4e499ec7 (radv: add initial non-conformant radv vulkan driver)
Signed-off-by: Dave Airlie <airlied@redhat.com>
(cherry picked from commit 8bf39307517a04263532e3c5a49b5be1f4a99032)
[Andres Gomez: resolve trivial conflicts]
Signed-off-by: Andres Gomez <agomez@igalia.com>
Conflicts:
	src/amd/vulkan/radv_device.c