Include <drm/drm_bridge.h> and forward declare struct platform device.
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/9534ca7dfba96580950e116c84ce0fa68fdf93a4.1709749576.git.jani.nikula@intel.com