MAINTAINERS: Update b44 maintainer.

Taking over as maintainer since Gary Zambrano is no longer working
for Broadcom.
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -2500,7 +2500,7 @@ S:	Supported
 F:	kernel/bpf/
 
 BROADCOM B44 10/100 ETHERNET DRIVER
-M:	Gary Zambrano <zambrano@broadcom.com>
+M:	Michael Chan <michael.chan@broadcom.com>
 L:	netdev@vger.kernel.org
 S:	Supported
 F:	drivers/net/ethernet/broadcom/b44.*