spi: spi-zynq: Do not check for 0 return after calling platform_get_irq()

It is not possible for platform_get_irq() to return 0. Use the
return value from platform_get_irq().

Signed-off-by: Ruan Jinjie <ruanjinjie@huawei.com>
Link: https://lore.kernel.org/r/20230802094357.981100-1-ruanjinjie@huawei.com


Signed-off-by: Mark Brown <broonie@kernel.org>