drm/vc4: hdmi: Support HDMI YUV output

BugLink: https://bugs.launchpad.net/bugs/1958146

In addition to the RGB444 output, the BCM2711 HDMI controller supports
the YUV444 and YUV422 output formats.

Let's add support for them in the driver, but still use RGB as the
preferred format.

Signed-off-by: Maxime Ripard <[email protected]>

(cherry picked from commit 04548bcf575fb1796431b578e81d145675029c29 rpi-5.15.y)
Signed-off-by: Juerg Haefliger <[email protected]>

Author: mripard