spi: spi-imx: Add check for spi_imx_setupxfer()

In the Linux kernel, the following vulnerability has been resolved: spi: spi-imx: Add check for spi_imx_setupxfer() Add check for the return value of spi_imx_setupxfer(). spi_imx->rx and spi_imx->tx function pointer can be NULL when spi_imx_setupxfer() return error, and make NULL pointer dereference. Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 Call trace: 0x0 spi_imx_pio_transfer+0x50/0xd8 spi_imx_transfer_one+0x18c/0x858 spi_transfer_one_message+0x43c/0x790 __spi_pump_transfer_message+0x238/0x5d4 __spi_sync+0x2b0/0x454 spi_write_then_read+0x11c/0x200