drm/i915/plane: rename intel_atomic_check_planes() to intel_plane_atomic_check()

Align with all the other atomic check functions.

Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://lore.kernel.org/r/57c59e33e31fbea564f61c2ffaa81e979e33f106.1750147992.git.jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>