spi: amlogic-spifc-a1: implement adjust_op_size()

This enhancement eliminates the need for a loop in the
amlogic_spifc_a1_exec_op() function and allows the SPI core to
dynamically divide transactions into appropriately sized chunks.

Signed-off-by: Martin Kurbanov <mmkurbanov@sberdevices.ru>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20230706110331.19794-2-mmkurbanov@sberdevices.ru


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