Check for a 'pci' prefix rather than a full match in get_addr_props

Summary:
Newer OPAL device trees, such as those on POWER9 systems, use 'pciex' for
device_type, not 'pci'. Rather than enumerating all possible variants, just
check for a 'pci' prefix.

Reviewed by: nwhitehorn, breno.leitao_gmail.com
Differential Revision: https://reviews.freebsd.org/D15817