drm: Replace instances of drm_format_info by drm_get_format_info

drm_get_format_info directly calls into drm_format_info, but takes directly
a struct drm_mode_fb_cmd2 pointer, instead of the fourcc directly. It's
shorter to not dereference it, and we can customise the behaviour at the
driver level if we want to, so let's switch to it where it makes sense.

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/5859d68664b8f0804a56e7386937f6db986b9e0f.1558002671.git-series.maxime.ripard@bootlin.com