drm/i915/cx0: remove unnecessary includes

There's nothing in the header that requires the bit or bitfield
headers. Remove.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/3e12f1d5ab17e501e4700044072fbb6dd9b2f459.1730146000.git.jani.nikula@intel.com