pci: enhance printf for leaked MSI[-X] vectors

When debugging leaked MSI/MSI-X vectors through LinuxKPI I found
the informational printf unhelpful. Rather than just stating we
leaked also tell how many MSI or MSI-X vectors we leak.

Sponsored-by: The FreeBSD Foundation
Reviewed-by: jhb
MFC-after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D29394