selftests: net: forwarding: change devlink resource support checking

As for the others, check help message output to find out if devlink
supports "resource" object.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/net/forwarding/devlink_lib.sh

@@ -32,7 +32,7 @@ DEVLINK_VIDDID=$(lspci -s $(echo $DEVLINK_DEV | cut -d"/" -f2) \
 ##############################################################################
 # Sanity checks
 
-devlink -j resource show "$DEVLINK_DEV" &> /dev/null
+devlink help 2>&1 | grep resource &> /dev/null
 if [ $? -ne 0 ]; then
 	echo "SKIP: iproute2 too old, missing devlink resource support"
 	exit 1