drm/edid: convert edid_is_zero() to edid_block_is_zero() for blocks

As edid_is_zero() is only ever used on EDID blocks, convert it to
edid_block_is_zero() with implicit block size.

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/5cc9387e22b4a61243df4053d1ebcc14b0007dc8.1649685475.git.jani.nikula@intel.com