drm/amd/display: Fix potential NULL and mem leak in create_links

Found by smatch:
drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc.c:148 create_links()
error: potential null dereference 'link->link_enc'.  (kzalloc returns
null)
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc.c

@@ -121,6 +121,10 @@ static bool create_links(
 			goto failed_alloc;
 		}
 
+		link->link_index = dc->link_count;
+		dc->links[dc->link_count] = link;
+		dc->link_count++;
+
 		link->ctx = dc->ctx;
 		link->dc = dc;
 		link->connector_signal = SIGNAL_TYPE_VIRTUAL;
@@ -128,6 +132,12 @@ static bool create_links(
 		link->link_id.id = CONNECTOR_ID_VIRTUAL;
 		link->link_id.enum_id = ENUM_ID_1;
 		link->link_enc = kzalloc(sizeof(*link->link_enc), GFP_KERNEL);
+
+		if (!link->link_enc) {
+			BREAK_TO_DEBUGGER();
+			goto failed_alloc;
+		}
+
 		link->link_status.dpcd_caps = &link->dpcd_caps;
 
 		enc_init.ctx = dc->ctx;
@@ -139,10 +149,6 @@ static bool create_links(
 		enc_init.encoder.id = ENCODER_ID_INTERNAL_VIRTUAL;
 		enc_init.encoder.enum_id = ENUM_ID_1;
 		virtual_link_encoder_construct(link->link_enc, &enc_init);
-
-		link->link_index = dc->link_count;
-		dc->links[dc->link_count] = link;
-		dc->link_count++;
 	}
 
 	return true;