spi: mpc5xxx-psc: Correct error check for devm_platform_get_and_ioremap_resource()

spi: mpc5xxx-psc: Correct error check for devm_platform_get_and_ioremap_resource()

devm_platform_get_and_ioremap_resource() may return pointer or error
pointer, never the NULL. Correct error check for it.

Fixes: 60a6c8257f41 ("spi: mpc5xxx-psc: Use platform resources instead of parsing DT properties")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230306183115.87314-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>