In order to support other SoC, it's required to distinguish
the 'control' timer register, from the 'rstout' register
that enables system reset on watchdog expiration.

To prevent a compatibility break, this commit adds a fallback
to a hardcoded RSTOUT address.
Reviewed-by: NGuenter Roeck <linux@roeck-us.net>
Tested-by: NSebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Tested-by: NWilly Tarreau <w@1wt.eu>
Signed-off-by: NEzequiel Garcia <ezequiel.garcia@free-electrons.com>
Acked-by: NWim Van Sebroeck <wim@iguana.be>
Tested-By: NJason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: NJason Cooper <jason@lakedaemon.net>