MAINTAINERS: add entry for TI ICSSG Ethernet driver

Add record for TI Industrial Communication Subsystem - Gigabit (ICSSG)
Ethernet driver.

Also add Roger and myself as maintainer.

Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>