mpi3mr: Move creation of watchdog to interupt config hook

Move creation of watchdog process from just before we configure the
interrupt config hook to into the config hook itself. This prevents it
from racing the config intr hook and doing an extra reset of the
card. This extra reset is usually harmless, but sometimes it can prevent
discovery of devices if done at just the wrong time. This can lead to no
disks being registered in a box full of disks, for example. Starting it
later eliminates this race, making discovery reliable.

Reviewed by: imp

(cherry picked from commit 7e02c7074c4c6df77b860e0dbcd032a2ea04b98b)