drm/edid: simplify block check when filtering invalid blocks

There's no need to handle complicated scenarios or debug log when
filtering blocks that have already been identified as invalid. Simplify
by adding an edid_block_valid() helper that operates on const data and
prints nothing.

(Finally, here's the justification for the previously added separate
edid_block_status_valid() function!)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/aa25131c3454c7dbc1e8fdb46549f3787bdf6354.1648752228.git.jani.nikula@intel.com