spi: spi-mpc52xx: switch to using gpiod API

This switches the driver to use gpiod API instead of legacy gpio API,
which will brings us close to removing of_get_gpio() and other
OF-specific old APIs.

No functional change intended beyond some differences in error messages.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/Yy07WbMAG4bPgYNd@google.com


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