drm/bridge: panel: drm_panel_bridge_remove: warn when called on non-panel bridge

This function is for panel_bridge instances only. The silent return when
invoked on other bridges might hide actual errors, so avoid them to go
unnoticed.

Reviewed-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250214-drm-assorted-cleanups-v7-4-88ca5827d7af@bootlin.com