drm/i915: Pass drm_frambuffer to intel_compute_page_offset()

intel_compute_page_offsets() gets passed a bunch of the framebuffer
metadate sepearately. Just pass the framebuffer itself to make life
simpler for the caller, and make it less likely they would make a
mistake in the order of the arguments (as most as just unsigned ints and
such).

We still pass the pitch explicitly since for 90/270 degree rotation
the caller has to pass in the right thing.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1455569699-27905-7-git-send-email-ville.syrjala@linux.intel.com