MAINTAINERS: add samples/pktgen to NETWORKING [GENERAL]

samples/pktgen is missing in the MAINTAINERS file.

Suggested-by: Antoine Tenart <atenart@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Message-ID: <20241018005301.10052-1-liuhangbin@gmail.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>

MAINTAINERS

@@ -16195,6 +16195,7 @@ F:	include/uapi/linux/rtnetlink.h
 F:	lib/net_utils.c
 F:	lib/random32.c
 F:	net/
+F:	samples/pktgen/
 F:	tools/net/
 F:	tools/testing/selftests/net/
 X:	Documentation/networking/mac80211-injection.rst