spi: Zap SOFT_SPI (non-dm)

- Deadline for DM migration already passed by months.
- Sent couple of zap patches and
- No response on dm conversation
hence removed the driver.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
3 files changed