Lets not introduce BIT() macro requirement for UAPI for now.

Fixes: 3fd3a6ff ("drm/i915: Simplify i915_reg_read_ioctl")
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171006104559.17312-1-joonas.lahtinen@linux.intel.com