[WATCHDOG] i6300esb.c: Restructure initialization of the device

The i6300ESB watchdog should be stopped before userspace has access to the
watchdog. So fix this and restructure the initialization sequence into:
	* See if we have a i6300 device
	* make sure that we have valid module parameters
	* Initialize the device
	* register the /dev/watchdog device so that userspace has access

Signed-off-by: Wim Van Sebroeck <wim@iguana.be>