drm/i915: Inline binary search

Instead of using bsearch library function make a local generator
macro out of it so the comparison callback can be inlined.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1475569769-31108-1-git-send-email-tvrtko.ursulin@linux.intel.com