net: axienet: In kconfig remove arch dependency for axi_emac

To enable xilinx axi_emac driver support on zynqmp ultrascale platform
(ARCH64) there are two choices, mention ARCH64 as a dependency list
and other is to check if this ARCH dependency list is really needed.
Later approach seems more reasonable, so remove the obsolete ARCH
dependency list for the axi_emac driver.

Sanity test done for microblaze, zynq and zynqmp ultrascale platform.

Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>