spi: stm32_qspi: Add transfer_one_message() spi callback

Add transfer_one_message() spi callback in order to use the QSPI interface
as a communication channel using up to 8 qspi lines (QSPI configured
in dual flash mode).
To enable this mode, both spi-rx-bus-width and spi-tx-bus-width must be
set to 8 and cs-qpios must be populated.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Link: https://lore.kernel.org/r/20220823075850.575043-3-patrice.chotard@foss.st.com
Signed-off-by: Mark Brown <broonie@kernel.org>