net: microchip: sparx5: clean up error checking in vcap_show_admin()

The vcap_decode_rule() never returns NULL.  There is no need to check
for that.  This code assumes that if it did return NULL we should
end abruptly and return success.  It is confusing.  Fix the check to
just be if (IS_ERR()) instead of if (IS_ERR_OR_NULL()).

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202309070831.hTvj9ekP-lkp@intel.com/
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Daniel Machon <daniel.machon@microchip.com>
Link: https://lore.kernel.org/r/b88eba86-9488-4749-a896-7c7050132e7b@moroto.mountain
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/microchip/vcap/vcap_api_debugfs.c

@@ -300,7 +300,7 @@ static int vcap_show_admin(struct vcap_control *vctrl,
 	vcap_show_admin_info(vctrl, admin, out);
 	list_for_each_entry(elem, &admin->rules, list) {
 		vrule = vcap_decode_rule(elem);
-		if (IS_ERR_OR_NULL(vrule)) {
+		if (IS_ERR(vrule)) {
 			ret = PTR_ERR(vrule);
 			break;
 		}