selftests: mptcp: join: fix dev in check_endpoint

There's a bug in pm_nl_check_endpoint(), 'dev' didn't be parsed correctly.
If calling it in the 2nd test of endpoint_tests() too, it fails with an
error like this:

 creation  [FAIL] expected '10.0.2.2 id 2 subflow dev dev' \
                     found '10.0.2.2 id 2 subflow dev ns2eth2'

The reason is '$2' should be set to 'dev', not '$1'. This patch fixes it.

Fixes: 69c6ce7b ("selftests: mptcp: add implicit endpoint test case")
Cc: stable@vger.kernel.org
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240329-upstream-net-20240329-fallback-mib-v1-2-324a8981da48@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/mptcp/mptcp_join.sh

@@ -729,7 +729,7 @@ pm_nl_check_endpoint()
 			[ -n "$_flags" ]; flags="flags $_flags"
 			shift
 		elif [ $1 = "dev" ]; then
-			[ -n "$2" ]; dev="dev $1"
+			[ -n "$2" ]; dev="dev $2"
 			shift
 		elif [ $1 = "id" ]; then
 			_id=$2
@@ -3610,6 +3610,8 @@ endpoint_tests()
 		local tests_pid=$!
 
 		wait_mpj $ns2
+		pm_nl_check_endpoint "creation" \
+			$ns2 10.0.2.2 id 2 flags subflow dev ns2eth2
 		chk_subflow_nr "before delete" 2
 		chk_mptcp_info subflows 1 subflows 1