drm/fourcc: Pass the format_info pointer to drm_format_plane_cpp

So far, the drm_format_plane_cpp function was operating on the format's
fourcc and was doing a lookup to retrieve the drm_format_info structure and
return the cpp.

However, this is inefficient since in most cases, we will have the
drm_format_info pointer already available so we shouldn't have to perform a
new lookup. Some drm_fourcc functions also already operate on the
drm_format_info pointer for that reason, so the API is quite inconsistent
there.

Let's follow the latter pattern and remove the extra lookup while being a
bit more consistent. In order to be extra consistent, also rename that
function to drm_format_info_plane_cpp and to a static function in the
header to match the current policy.

Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/32aa13e53dbc98a90207fd290aa8e79f785fb11e.1558002671.git-series.maxime.ripard@bootlin.com

drivers/gpu/drm/arm/malidp_hw.c

@@ -382,7 +382,8 @@ static void malidp500_modeset(struct malidp_hw_device *hwdev, struct videomode *
 
 int malidp_format_get_bpp(u32 fmt)
 {
-	int bpp = drm_format_plane_cpp(fmt, 0) * 8;
+	const struct drm_format_info *info = drm_format_info(fmt);
+	int bpp = drm_format_info_plane_cpp(info, 0) * 8;
 
 	if (bpp == 0) {
 		switch (fmt) {