selftests: mptcp: ignore mptcp_diag binary

JIRA: https://issues.redhat.com/browse/RHEL-115576
Upstream Status: net-next.git commit b44a4c2

commit b44a4c2
Author: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Date:   Fri Mar 28 15:27:19 2025 +0100

    selftests: mptcp: ignore mptcp_diag binary

    A new binary is now generated by the MPTCP selftests: mptcp_diag.

    Like the other binaries from this directory, there is no need to track
    this in Git, it should then be ignored.

    Fixes: 00f5e33 ("selftests: mptcp: Add a tool to get specific msk_info")
    Reviewed-by: Mat Martineau <martineau@kernel.org>
    Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
    Link: https://patch.msgid.link/20250328-net-mptcp-misc-fixes-6-15-v1-4-34161a482a7f@kernel.org
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Davide Caratti <dcaratti@redhat.com>

Author: dcaratti

tools/testing/selftests/net/mptcp/.gitignore

@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-only
 mptcp_connect
+mptcp_diag
 mptcp_inq
 mptcp_sockopt
 pm_nl_ctl