drm/i915/bios: fix header define name for intel_bios.h

Just for OCD.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/730e41760133dbaa1e3ab1b91631ada18676810c.1450702954.git.jani.nikula@intel.com