Since the commit 1289e96797 ("sandbox: spi: Drop command-line SPI
option"), "--spi_sf" command line option is no longer supported.
So update the following documents to sync them up with the change.
doc/arch/sandbox.rst
doc/SPI/README.sandbox-spi
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>