drm/i915: Use drm_framebuffer_plane_{width,height}() where possible

Replace drm_format_plane_{width,height}() usage with
drm_framebuffer_plane_{width,height}() to avoid the lookup of the format
info.

Cc: intel-gfx@lists.freedesktop.org
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1479498793-31021-31-git-send-email-ville.syrjala@linux.intel.com


Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>