watchdog: sp5100_tco: Match PCI device early

Match PCI device in module init function, not in the probe function.
It is pointless trying to probe if we can determine early that the device
is not supported.

Cc: Zoltán Böszörményi <zboszor@pr.hu>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>