drm/edid: VSDB yCBCr420 Deep Color mode bit definitions

HDMI Forum VSDB YCBCR420 deep color capability bits are 2:0. Correct
definitions in the header for the mask to work correctly.

Fixes: e6a9a2c3 ("drm/edid: parse ycbcr 420 deep color information")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107893


Cc: <stable@vger.kernel.org> # v4.14+
Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1538776335-12569-1-git-send-email-clinton.a.taylor@intel.com