MAINTAINERS: add arcnet and take maintainership

Add entry for arcnet to MAINTAINERS file and add myself as the
maintainer of the subsystem.
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Cc: davem@davemloft.net
Cc: joe@perches.com
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -808,6 +808,13 @@ S:	Maintained
 F:	drivers/video/fbdev/arcfb.c
 F:	drivers/video/fbdev/core/fb_defio.c
 
+ARCNET NETWORK LAYER
+M:	Michael Grzeschik <m.grzeschik@pengutronix.de>
+L:	netdev@vger.kernel.org
+S:	Maintained
+F:	drivers/net/arcnet/
+F:	include/uapi/linux/if_arcnet.h
+
 ARM MFM AND FLOPPY DRIVERS
 M:	Ian Molton <spyro@f2s.com>
 S:	Maintained