drm/i915: fix open-coded DIV_ROUND_UP

Use the nice Kernel macro, it makes the code much more readable.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --cc drivers/gpu/drm/i915/i915_gem.c
Simple merge

diff --cc drivers/gpu/drm/i915/intel_fbdev.c
Simple merge