Fix xae(4) driver attachement on the Government Furnished Equipment (GFE)

Fix xae(4) driver attachement on the Government Furnished Equipment (GFE)
riscv cores.

GFE cores come with standard DTS file that lacks standard 'dmas ='
property, which means xae(4) could not find a DMA controller to use.

The 'dmas' property could not be added to the DTS file because the
ethernet controller and DMA engine parts in Linux are implemented
in a single driver.

Instead of 'dmas' property the standard Xilinx 'axistream-connected'
property is provided, so fallback to use it instead.

Suggested by:	James Clarke <jrtc27@jrtc27.com>
Reviewed by:	James Clarke <jrtc27@jrtc27.com>
Sponsored by:	DARPA, AFRL