pvscsi: maximum target number is one less than number of targets

Fix the number of targets we inquiry to be one less than the maximum
number of targets adapter reports. This gets rid of the errors reported
on VMware Workstation:

(probe36:pvscsi0:0:65:0): INQUIRY. CDB: 12 00 00 00 24 00
(probe36:pvscsi0:0:65:0): CAM status: CCB request completed with an error

While here, print the maximum number of targets.

Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D39867