net: Remove Xilinx ll_temac driver

ll_temac driver was used by Xilinx Microblaze big endian and
Xilinx ppc405/ppc440 SoCs.

ppc support was removed by: "powerpc: remove 4xx support"
(sha1: 98f705c9)
and Microblaze BE is not tested for a long time that's why this driver
can be removed because none is going to updated it to DM anyway.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>