ethernet: qualcomm: use spi instead of spi_device

All spi based drivers have an instance of struct spi_device
as spi. This patch renames spi_device to spi to synchronize
with all the drivers.

Signed-off-by: Varka Bhadram <varkab@cdac.in>
Signed-off-by: David S. Miller <davem@davemloft.net>