netdevsim: add Makefile for selftests

Add a Makefile for netdevsim selftests and add selftests path to
MAINTAINERS
Signed-off-by: David Wei <dw@davidwei.uk>
Link: https://lore.kernel.org/r/20240130214620.3722189-5-dw@davidwei.ukSigned-off-by: Jakub Kicinski <kuba@kernel.org>

MAINTAINERS

@@ -15087,6 +15087,7 @@ NETDEVSIM
 M:	Jakub Kicinski <kuba@kernel.org>
 S:	Maintained
 F:	drivers/net/netdevsim/*
+F:	tools/testing/selftests/drivers/net/netdevsim/*
 
 NETEM NETWORK EMULATOR
 M:	Stephen Hemminger <stephen@networkplumber.org>

tools/testing/selftests/drivers/net/netdevsim/Makefile

+# SPDX-License-Identifier: GPL-2.0+ OR MIT
+
+TEST_PROGS = devlink.sh \
+	devlink_in_netns.sh \
+	devlink_trap.sh \
+	ethtool-coalesce.sh \
+	ethtool-fec.sh \
+	ethtool-pause.sh \
+	ethtool-ring.sh \
+	fib.sh \
+	hw_stats_l3.sh \
+	nexthop.sh \
+	psample.sh \
+	tc-mq-visibility.sh \
+	udp_tunnel_nic.sh \
+
+include ../../../lib.mk