drm/format-helper: Add drm_fb_build_fourcc_list() helper

Add drm_fb_build_fourcc_list() function that builds a list of supported
formats from native and emulated ones. Helpful for all drivers that do
format conversion as part of their plane updates. Update current caller.

v3:
	* improve warnings on ignored formats (Sam)
v2:
	* use u32 instead of uint32_t (Sam)
	* print a warning if output array is too small (Sam)
	* comment fixes (Sam)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220905141648.22013-5-tzimmermann@suse.de