spi: Fix OCTAL mode support

[ Upstream commit d6a711a8 ]

Add OCTAL mode support.
Issue detected using "--octal" spidev_test's option.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Link: https://msgid.link/r/20240618132951.2743935-4-patrice.chotard@foss.st.com


Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>