watchdog: orion_wdt: use timer1 as a pretimeout

The orion watchdog can either reset the CPU or generate an interrupt.
The interrupt would be useful for debugging as it provides panic()
output about the watchdog expiry, however if the interrupt is used the
watchdog can't reset the CPU in the event of being stuck in a loop with
interrupts disabled or if the CPU is prevented from accessing memory
(e.g. an unterminated DMA).

The Armada SoCs have spare timers that aren't currently used by the
Linux kernel. We can use timer1 to provide a pre-timeout ahead of the
watchdog timer and provide the possibility of gathering debug before the
reset triggers.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20190829215224.27956-1-chris.packham@alliedtelesis.co.nz
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>