spi: uniphier: Fix completion initialization order before devm_request_irq()

In the Linux kernel, the following vulnerability has been resolved: spi: uniphier: Fix completion initialization order before devm_request_irq() The driver calls devm_request_irq() before initializing the completion used by the interrupt handler. Because the interrupt may occur immediately after devm_request_irq(), the handler may execute before init_completion(). This may result in calling complete() on an uninitialized completion, causing undefined behavior. This has been observed with KASAN. Fix this by initializing the completion before registering the IRQ.