drm/edid: Don't clear YUV422 if using deep color

The current code, when parsing the EDID Deep Color depths, that the
YUV422 cannot be used, referring to the HDMI 1.3 Specification.

This specification, in its section 6.2.4, indeed states:

  For each supported Deep Color mode, RGB 4:4:4 shall be supported and
  optionally YCBCR 4:4:4 may be supported.

  YCBCR 4:2:2 is not permitted for any Deep Color mode.

This indeed can be interpreted like the code does, but the HDMI 1.4
specification further clarifies that statement in its section 6.2.4:

  For each supported Deep Color mode, RGB 4:4:4 shall be supported and
  optionally YCBCR 4:4:4 may be supported.

  YCBCR 4:2:2 is also 36-bit mode but does not require the further use
  of the Deep Color modes described in section 6.5.2 and 6.5.3.

This means that, even though YUV422 can be used with 12 bit per color,
it shouldn't be treated as a deep color mode.

This deviates from the interpretation of the code and comment, so let's
fix those.

Fixes: d0c94692 ("drm/edid: Parse and handle HDMI deep color modes.")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>