genetlink: add explicit ordering break check for split ops

Currently, if cmd in the split ops array is of lower value than the
previous one, genl_validate_ops() continues to do the checks as if
the values are equal. This may result in non-obvious WARN_ON() hit in
these check.

Instead, check the incorrect ordering explicitly and put a WARN_ON()
in case it is broken.
Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20230720111354.562242-1-jiri@resnulli.usSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/netlink/genetlink.c

@@ -593,8 +593,12 @@ static int genl_validate_ops(const struct genl_family *family)
 			return -EINVAL;
 
 		/* Check sort order */
-		if (a->cmd < b->cmd)
+		if (a->cmd < b->cmd) {
 			continue;
+		} else if (a->cmd > b->cmd) {
+			WARN_ON(1);
+			return -EINVAL;
+		}
 
 		if (a->internal_flags != b->internal_flags ||
 		    ((a->flags ^ b->flags) & ~(GENL_CMD_CAP_DO |