drm/i915: Fix coding style for RPS

Introduced:
commit b8a5ff8d
Author: Jeff McGee <jeff.mcgee@intel.com>
Date:   Tue Feb 4 11:37:01 2014 -0600

    drm/i915: Update rps interrupt limits

Cc: Jeff McGee <jeff.mcgee@intel.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>