Input: psxpad-spi - add a check for the return value of spi_setup()

The probe function in the psxpad-spi driver calls spi_setup()
but fails to check its return value. If the SPI bus setup fails,
the driver will still load successfully, resulting in potential
error in later I/O operations.

Add a check for the return value of spi_setup() and return
an error on failure.

Fixes: 8be193c7 ("Input: add support for PlayStation 1/2 joypads connected via SPI")
Signed-off-by: Haotian Zhang <vulab@iscas.ac.cn>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>