Add support for using with both wl12xx and wl18xx.
- all wilink family needs special init command for entering wspi mode.
extra clock cycles should be sent after the spi init command while the
cs pin is high.
- Use inverted chip select for sending a dummy 4 bytes command that
completes the init stage.
Signed-off-by: Eyal Reizer <eyalr@ti.com> Acked-by: Rob Herring <robh@kernel.org> Signed-off-by: Kalle Valo <kvalo@codeaurora.org>