drm: bridge: cdns-mhdp8546: Fix possible null pointer dereference

In the Linux kernel, the following vulnerability has been resolved: drm: bridge: cdns-mhdp8546: Fix possible null pointer dereference In cdns_mhdp_atomic_enable(), the return value of drm_mode_duplicate() is assigned to mhdp_state->current_mode, and there is a dereference of it in drm_mode_set_name(), which will lead to a NULL pointer dereference on failure of drm_mode_duplicate(). Fix this bug add a check of mhdp_state->current_mode.