amd-xgbe: Add support for per DMA channel interrupts

This patch provides support for interrupts that are generated by the
Tx/Rx DMA channel pairs of the device.  This allows for Tx and Rx
processing to run across multiple processsors.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>