drm/radeon: properly handle mc_stop/mc_resume on evergreen+ (v2)

- Stop the displays from accessing the FB
- Block CPU access
- Turn off MC client access

This should fix issues some users have seen, especially
with UEFI, when changing the MC FB location that result
in hangs or display corruption.

v2: fix crtc enabled check noticed by Luca Tettamanti

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 18c38d1..132429e 100644
--- a/drivers/gpu/drm/radeon/radeon_asic.h
+++ b/drivers/gpu/drm/radeon/radeon_asic.h
@@ -389,6 +389,7 @@
 struct evergreen_mc_save {
 	u32 vga_render_control;
 	u32 vga_hdp_control;
+	bool crtc_enabled[RADEON_MAX_CRTCS];
 };
 
 void evergreen_pcie_gart_tlb_flush(struct radeon_device *rdev);