MAINTAINERS: Add entry for Altera Triple Speed Ethernet Driver

Add a MAINTAINERS entry covering the Altera Triple Speed
Ethernet Driver, with support for the MSGDMA and SGDMA
soft DMA IP components.

Signed-off-by: Vince Bridgers <vbridgers2013@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>