drm/radeon: add basic zmask/hiz support (v4)

This interface allows userspace to request hyperz support, it probably
needs more locking, and really reporting that you can have hyperz is racy
since someone else might get it before you do.

v2: modify so we pass 0 valued packets to let DDX/r300c keep working.
also fixed incorrect 0x4f1c reference.

v3: fixup zb_bw_cntl so older drivers keep working

v4: add locking, fixup SC_HYPERZ_EN - patch stream to disable hiz

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
index c84f9a3..368fecf0 100644
--- a/drivers/gpu/drm/radeon/radeon.h
+++ b/drivers/gpu/drm/radeon/radeon.h
@@ -1098,6 +1098,8 @@
 
 	bool powered_down;
 	struct notifier_block acpi_nb;
+	/* only one userspace can use Hyperz features at a time */
+	struct drm_file *hyperz_filp;
 };
 
 int radeon_device_init(struct radeon_device *rdev,