spi: rockchip-sfc: Fix double-free in remove() callback

In the Linux kernel, the following vulnerability has been resolved: spi: rockchip-sfc: Fix double-free in remove() callback The driver uses devm_spi_register_controller() for registration, which automatically unregisters the controller via devm cleanup when the device is removed. The manual call to spi_unregister_controller() in the remove() callback can lead to a double-free. And to make sure controller is unregistered before DMA buffer is unmapped, switch to use spi_register_controller() in probe().