drm/connector: Change DRM card alias from underscore to hyphen

Apparently aliases are only allowed lower case and hyphens,
so swap the use of underscore to hyphen.

Fixes: 3aa1f24 ("drm: Look for an alias for the displays to use as the DRM device name")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

drivers/gpu/drm/drm_connector.c

@@ -112,7 +112,7 @@ static struct drm_conn_prop_enum_list drm_connector_enum_list[] = {
 };
 
 #define MAX_DT_NODE_NAME_LEN	20
-#define DT_DRM_NODE_PREFIX	"drm_"
+#define DT_DRM_NODE_PREFIX	"drm-"
 
 static void drm_connector_get_of_name(int type, char *node_name, int length)
 {