Documentation: networking: Add Altera Ethernet (TSE) Documentation

This patch adds a bindings description for the Altera Triple Speed Ethernet
(TSE) driver. The bindings support the legacy SGDMA soft IP as well as the
preferred MSGDMA soft IP. The TSE can be configured and synthesized in soft
logic using Altera's Quartus toolchain. Please consult the bindings document
for supported options.
Signed-off-by: Vince Bridgers <vbridgers2013@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>