drm/edid: fix edid field name

Byte 26 in a edid struct is supposed to be "Blue and white
least-significant 2 bits", not "black and white". Rename the field
accordingly. This field is not used anywhere, so just renaming it here
for correctness.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Simon Ser <contact@emersion.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/20210811205818.156100-1-lucas.demarchi@intel.com