net: ll_temac: remove virt_to_bus call

The virt_to_bus call should not be used any longer as it's
considered illegal. The driver has the physical address of
the buffer in the descriptor such that it's not necessary
anyway.

Signed-off-by: John Linn <john.linn@xilinx.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>