dm: spi: Remove SPI_INIT feature

dm: spi: Remove SPI_INIT feature

This feature provides for init of a single SPI port for the soft SPI
feature. It is not really compatible with driver model since it assumes a
single SPI port. Also, inserting SPI init into the driver by means of
a #define is not very nice.

This feature is not used by any active boards, so let's remove it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>