spi: wpcm-fiu: Fix potential NULL pointer dereference in wpcm_fiu_probe()

In the Linux kernel, the following vulnerability has been resolved: spi: wpcm-fiu: Fix potential NULL pointer dereference in wpcm_fiu_probe() platform_get_resource_byname() can return NULL, which would cause a crash when passed the pointer to resource_size(). Move the fiu->memory_size assignment after the error check for devm_ioremap_resource() to prevent the potential NULL pointer dereference.