spi: stm32-qspi: add automatic poll status feature

STM32 QSPI is able to automatically poll a specified register inside the
memory and relieve the CPU from this task.

As example, when erasing a large memory area, we got cpu load
equal to 50%. This patch allows to perform the same operation
with a cpu load around 2%.

Signed-off-by: Christophe Kerello <christophe.kerello@foss.st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Link: https://lore.kernel.org/r/20210518162754.15940-4-patrice.chotard@foss.st.com
Signed-off-by: Mark Brown <broonie@kernel.org>