net: xilinx: temac: Relax Kconfig dependencies

Similar to axienet, the temac driver is now architecture agnostic, and
can be at least compiled for several architectures.
Especially the fact that this is a soft IP for implementing in FPGAs
makes the current restriction rather pointless, as it could literally
appear on any architecture, as long as an FPGA is connected to the bus.

The driver hasn't been actually tried on any hardware, it is just a
drive-by patch when doing the same for axienet (a similar patch for
axienet is already merged).

This (temac and axienet) have been compile-tested for:
alpha hppa64 microblaze mips64 powerpc powerpc64 riscv64 s390 sparc64
(using kernel.org cross compilers).

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>