MAINTAINERS: add myself as maintainer of marvell10g driver

Add myself as maintainer of the marvell10g ethernet PHY driver, in
addition to Russell King.
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -10695,6 +10695,7 @@ F:	include/linux/mv643xx.h
 
 MARVELL MV88X3310 PHY DRIVER
 M:	Russell King <linux@armlinux.org.uk>
+M:	Marek Behun <marek.behun@nic.cz>
 L:	netdev@vger.kernel.org
 S:	Maintained
 F:	drivers/net/phy/marvell10g.c