vxge: update MAINTAINERS

Exar has exited the 10G Ethernet NIC market, orphaning both the s2io and
vxge drivers.  With the promise of free hardware, I'll take over
maintainership.

Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: David S. Miller <davem@davemloft.net>