Break KSZ9477 DSA driver into two files in preparation to add more KSZ
switch drivers.
Add common functions in ksz_common.h so that other KSZ switch drivers
can access code in ksz_common.c.
Add ksz_spi.h for common functions used by KSZ switch SPI drivers.
Signed-off-by: NTristram Ha <Tristram.Ha@microchip.com>
Reviewed-by: NWoojung Huh <Woojung.Huh@microchip.com>
Reviewed-by: NPavel Machek <pavel@ucw.cz>
Reviewed-by: NFlorian Fainelli <f.fainelli@gmail.com>
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>