anv/allocator: Enable snooping on block pool and anv_bo_pool BOs.

anv/allocator: Enable snooping on block pool and anv_bo_pool BOs.

We are not going to use userptr for anv block pool BOs anymore. However,
so far we have been relying on the fact that userptr BOs are snooped on
non-llc platforms. Let's make sure that the block pool BOs are still
snooped, and we can also remove the clflush'ing that we do on all state
buffers.

And since we plan to remove the flushes, set the anv_bo_pool BOs to
cached (snooped on non-LLC platforms) too. For LLC platforms, they are
all cached by default, so this becomes a no-op.

v5:
 - Add snooping to anv_bo_pool BOs too (Jason).
 - Remove anv_gem_set_domain.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>