drm/msm: Fix return type of mdp4_lvds_connector_mode_valid

drm/msm: Fix return type of mdp4_lvds_connector_mode_valid

The mode_valid field in drm_connector_helper_funcs is expected to be of
type:
enum drm_mode_status (* mode_valid) (struct drm_connector *connector,
                                     struct drm_display_mode *mode);

The mismatched return type breaks forward edge kCFI since the underlying
function definition does not match the function hook definition.

The return type of mdp4_lvds_connector_mode_valid should be changed from
int to enum drm_mode_status.

Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1703
Cc: llvm@lists.linux.dev
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Fixes: 3e87599b68e7 ("drm/msm/mdp4: add LVDS panel support")
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Patchwork: https://patchwork.freedesktop.org/patch/502878/
Link: https://lore.kernel.org/r/20220913205551.155128-1-nhuck@google.com
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>