usb: cdns3: remove dead code

Smatch reports the following error:

drivers/usb/cdns3/cdns3-plat.c:113 cdns3_plat_probe() warn:
platform_get_irq() does not return zero

From the document, platform_get_irq_byname_optional only returns
non-zero value, and negative value on failure.

Fix this by removing the zero value checking.

Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
Link: https://lore.kernel.org/r/20220926135922.24541-1-dzm91@hust.edu.cn


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