spi: spidev: Replace OF specific code by device property API

Instead of calling the OF specific APIs, use device property ones.

It also prevents misusing PRP0001 in ACPI when trying to instantiate
spidev directly. We only support special SPI test devices there.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220323140215.2568-4-andriy.shevchenko@linux.intel.com


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