tty: serial: xilinx_uartps: Do not check for 0 return after calling platform_get_irq()

Since commit a85a6c86 ("driver core: platform: Clarify that
IRQ 0 is invalid"), there is no 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/20230803091712.596987-1-ruanjinjie@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>