drm/imx: imx-tve: Fix return type of imx_tve_connector_mode_valid

drm/imx: imx-tve: Fix return type of imx_tve_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 imx_tve_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>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220913205544.155106-1-nhuck@google.com