pixel-formats: Add P030

Which is used on the RPi4/5 by the HEVC HW decoder for 10bit content.

Note that this is not enough to make KMS offloading work as the
decoder uses the BROADCOM_SAND128 modifier which - for now - requires
manual/unusual handling (i.e. this requires going through GL).

Signed-off-by: Robert Mader <robert.mader@collabora.com>