Fix mptutil's method for locating disk devices attached to a specific
mpt(4) controller. Previously, the code assumed that multiple match
patterns provided to an XPT_DEV_MATCH request were ANDed together.
Instead, they are ORed. Instead, to match peripherals for a specific bus,
one query needs to be performed to lookup the path ID of the bus. A second
query can then be performed matching peripherals attached to that path.
This approach also makes the code a bit cleaner as the returned match
results do not mix bus and perphierals.

Reported by: several folks
MFC after: 1 week