drm: Export drm_plane_has_format()

Export drm_plane_has_format() so that drivers can use it.

v2: add kerneldoc

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240619113144.1616-1-ville.syrjala@linux.intel.com


Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Daniel Stone <daniels@collabora.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>