drm/bridge: tc358767: Fix return value on error case

If the hpd_pin is invalid, the driver returns 'ret'. But 'ret' contains
0, instead of an error value.

Return -EINVAL instead.

Fixes: f25ee501

 ("drm/bridge: tc358767: add IRQ and HPD support")
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231103-uninit-fixes-v2-4-c22b2444f5f5@ideasonboard.com