drm: Use drm_format_info() in DRM core code

Replace calls to the drm_format_*() helper functions with direct use of
the drm_format_info structure. This improves efficiency by removing
duplicate lookups.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1476744081-24485-4-git-send-email-laurent.pinchart@ideasonboard.com