genirq: Fix misleading synchronize_irq() documentation

commit 1d21f2af upstream.

The function might sleep, so it cannot be called from interrupt
context. Not even with care.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/20190628111440.189241552@linutronix.de


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