MFC: r153342
MFC: r153342

Fix a bug introduced in r1.5/153057 (MFC'ed in r1.4.8.1/172460); for
retrieving the device_t of the parent bridge of a PCI-PCI bridge we
need two device_get_parent().

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase