pci: Add pci_find_class_from

pci_find_class_from help finding one or multiple device matching
a class and subclass.
If the from argument is not null we will first loop in the device list
until we find the matching device and only then start to check if the
class/subclass matches.

Reviewed by: jhb
Differential Revision: https://reviews.freebsd.org/D27549