genirq: Set irq masked state when initializing irq_desc

The irq default state is set to disabled when allocating irq desc, but the
masked state flag is not set. This is inconsistent vs. the state tracking
logic which is used to prevent unnecessary calls to hardware level irq chip
functions.

Set the masked state flag as well.

Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: tfiga@chromium.org
Cc: briannorris@chromium.org
Cc: dianders@chromium.org
Link: http://lkml.kernel.org/r/1498476814-12563-1-git-send-email-jeffy.chen@rock-chips.com