This driver (currently) only takes control of the switch chip over
SPI and configures it to route packages around when connected to a
CPU port. But Vitesse chip support also parallel interface.

This patch split driver into two parts: core and spi. It is required
for add support to another managing interface.
Tested-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NPawel Dembicki <paweldembicki@gmail.com>
Reviewed-by: NLinus Walleij <linus.walleij@linaro.org>
Reviewed-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>