drm/displayid: allow data blocks with 0 payload length

The DisplayID specifications explicitly call out 0 as a valid payload
length for data blocks. The mere presence of a data block, or the
information coded in the block specific data (bits 7:3 in offset 1), may
be enough to convey the necessary information.
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/d562dff99ba7c92accb654a99b433bed471e8507.1617024940.git.jani.nikula@intel.com

drivers/gpu/drm/drm_displayid.c

@@ -77,8 +77,7 @@ displayid_iter_block(const struct displayid_iter *iter)
 	block = (const struct displayid_block *)&iter->section[iter->idx];
 
 	if (iter->idx + sizeof(*block) <= iter->length &&
-	    iter->idx + sizeof(*block) + block->num_bytes <= iter->length &&
-	    block->num_bytes > 0)
+	    iter->idx + sizeof(*block) + block->num_bytes <= iter->length)
 		return block;
 
 	return NULL;