drm/vrr: Set VRR capable prop only if it is attached to connector

stable inclusion
from stable-v5.10.107
commit 0ba557d330946c23559aaea2d51ea649fdeca98a
bugzilla: https://gitee.com/openeuler/kernel/issues/I574A2

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0ba557d330946c23559aaea2d51ea649fdeca98a

--------------------------------

[ Upstream commit 62929726 ]

VRR capable property is not attached by default to the connector
It is attached only if VRR is supported.
So if the driver tries to call drm core set prop function without
it being attached that causes NULL dereference.

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: NManasi Navare <manasi.d.navare@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220225013055.9282-1-manasi.d.navare@intel.comSigned-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/gpu/drm/drm_connector.c

@@ -2155,6 +2155,9 @@ EXPORT_SYMBOL(drm_connector_attach_max_bpc_property);
 void drm_connector_set_vrr_capable_property(
 		struct drm_connector *connector, bool capable)
 {
+	if (!connector->vrr_capable_property)
+		return;
+
 	drm_object_property_set_value(&connector->base,
 				      connector->vrr_capable_property,
 				      capable);