drm/connector: Fix typo in documentation

Commit 4adc33f3 ("drm/edid: Split deep color modes between RGB and
YUV444") introduced two new variables in struct drm_display_info and
their documentation, but the documentation part had a typo resulting in
a doc build warning.

Fixes: 4adc33f3

 ("drm/edid: Split deep color modes between RGB and YUV444")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Simon Ser <contact@emersion.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/20220202094340.875190-1-maxime@cerno.tech