net: ksz9477: add support for KSZ GbE switches using SPI bus

The Microchip KSZ Gigabit Ethernet Switches support
SGMII/RGMII/MII/RMII with register access via SPI, I2C, or MDIO.

Since this driver is now able to check the underlying bus type,
handle the case when the SPI bus is used.

The SPI bus is only used for 8/16/32 wide access of registers.

Reword Kconfig option to include SPI bus support.

Signed-off-by: Romain Naour <romain.naour@smile.fr>
2 files changed