platform: remove useless if-branch in __platform_get_irq_byname()

When CONFIG_OF_IRQ is not enabled, there will be a stub method that always
returns 0 when getting IRQ. Thus, the if-branch can be removed safely.

Signed-off-by: Soha Jin <soha@lohu.info>
Link: https://lore.kernel.org/r/20221111094542.270540-1-soha@lohu.info


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