drm/radeon: hook up backlight functions for CI and KV family.

Fixes crashes when handling atif events due to the lack of a
callback being registered.

Signed-off-by: Samuel Li <samuel.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/radeon/radeon_asic.c

@@ -2015,6 +2015,8 @@ static struct radeon_asic ci_asic = {
 		.bandwidth_update = &dce8_bandwidth_update,
 		.get_vblank_counter = &evergreen_get_vblank_counter,
 		.wait_for_vblank = &dce4_wait_for_vblank,
+		.set_backlight_level = &atombios_set_backlight_level,
+		.get_backlight_level = &atombios_get_backlight_level,
 		.hdmi_enable = &evergreen_hdmi_enable,
 		.hdmi_setmode = &evergreen_hdmi_setmode,
 	},
@@ -2114,6 +2116,8 @@ static struct radeon_asic kv_asic = {
 		.bandwidth_update = &dce8_bandwidth_update,
 		.get_vblank_counter = &evergreen_get_vblank_counter,
 		.wait_for_vblank = &dce4_wait_for_vblank,
+		.set_backlight_level = &atombios_set_backlight_level,
+		.get_backlight_level = &atombios_get_backlight_level,
 		.hdmi_enable = &evergreen_hdmi_enable,
 		.hdmi_setmode = &evergreen_hdmi_setmode,
 	},