drm/radeon: add get_allowed_info_register for r6xx/r7xx

Registers that can be fetched from the info ioctl.

Tested-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/radeon_asic.h b/drivers/gpu/drm/radeon/radeon_asic.h
index 4259daf..3e1346d 100644
--- a/drivers/gpu/drm/radeon/radeon_asic.h
+++ b/drivers/gpu/drm/radeon/radeon_asic.h
@@ -384,6 +384,8 @@
 		      struct radeon_ring *ring);
 void r600_gfx_set_wptr(struct radeon_device *rdev,
 		       struct radeon_ring *ring);
+int r600_get_allowed_info_register(struct radeon_device *rdev,
+				   u32 reg, u32 *val);
 /* r600 irq */
 int r600_irq_process(struct radeon_device *rdev);
 int r600_irq_init(struct radeon_device *rdev);