selftests: forwarding: lib: Split out setup_wait_dev()

Split out of setup_wait() a function setup_wait_dev() that waits for a
single device. This gives tests the opportunity to wait for a selected
device after they tinkered with its upness.
Signed-off-by: NPetr Machata <petrm@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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

@@ -185,11 +185,12 @@ log_info()
 	echo "INFO: $msg"
 }
 
-setup_wait()
+setup_wait_dev()
 {
-	for i in $(eval echo {1..$NUM_NETIFS}); do
+	local dev=$1; shift
+
 	while true; do
-			ip link show dev ${NETIFS[p$i]} up \
+		ip link show dev $dev up \
 			| grep 'state UP' &> /dev/null
 		if [[ $? -ne 0 ]]; then
 			sleep 1
@@ -197,6 +198,12 @@ setup_wait()
 			break
 		fi
 	done
+}
+
+setup_wait()
+{
+	for i in $(eval echo {1..$NUM_NETIFS}); do
+		setup_wait_dev ${NETIFS[p$i]}
 	done
 
 	# Make sure links are ready.