selftests: net: dsa: Add a Makefile which installs the selftests

Add a Makefile which takes care of installing the selftests in
tools/testing/selftests/drivers/net/dsa. This can be used to install all
DSA specific selftests and forwarding.config using the same approach as
for the selftests in tools/testing/selftests/net/forwarding.
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20220727191642.480279-1-martin.blumenstingl@googlemail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/drivers/net/dsa/Makefile

+# SPDX-License-Identifier: GPL-2.0+ OR MIT
+
+TEST_PROGS = bridge_locked_port.sh \
+	bridge_mdb.sh \
+	bridge_mld.sh \
+	bridge_vlan_aware.sh \
+	bridge_vlan_mcast.sh \
+	bridge_vlan_unaware.sh \
+	local_termination.sh \
+	no_forwarding.sh \
+	test_bridge_fdb_stress.sh
+
+TEST_PROGS_EXTENDED := lib.sh
+
+TEST_FILES := forwarding.config
+
+include ../../../lib.mk