drm/i915: Pass stride to rotate_pages()

Pass stride in addition to width and height to rotate_pages(). For now
width and stride are the same, but once framebuffer offsets enter the
scene that may no longer be the case.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1453316739-13296-3-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>