drm/i915: make intel_bios.h self-contained

Just a types include required.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/15b8dea022bd80198f91c59f8ad793ebd8fc04f0.1556540889.git.jani.nikula@intel.com