tty: serial: atmel: rework interrupt and wakeup handling

tty: serial: atmel: rework interrupt and wakeup handling

The IRQ line connected to the DBGU UART is often shared with a timer device
which request the IRQ with IRQF_NO_SUSPEND.

Since the UART driver is correctly disabling IRQs when entering suspend
we can safely request the IRQ with IRQF_COND_SUSPEND so that irq core
will not complain about mixing IRQF_NO_SUSPEND and !IRQF_NO_SUSPEND.

Rework the interrupt handler to wake the system up when an interrupt
happens on the DEBUG_UART while the system is suspended.

Signed-off-by: Boris Brezillon <[email protected]>
Reviewed-by: Alexandre Belloni <[email protected]>
Acked-by: Nicolas Ferre <[email protected]>
Acked-by: Mark Rutland <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>