x86/pci, x86/amd_nb: Add Hygon Dhyana support to PCI and northbridge

Hygon's PCI vendor ID is 0x1d94, and there are PCI devices
0x1450/0x1463/0x1464 for the host bridge on the Hygon Dhyana platform.
Add Hygon Dhyana support to the PCI and northbridge subsystems by using
the code path of AMD family 17h.

 [ bp: Massage commit message, sort local vars into reverse xmas tree
   order and move the amd_northbridges.num check up. ]

Signed-off-by: Pu Wen <puwen@hygon.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>	# pci_ids.h
Cc: tglx@linutronix.de
Cc: mingo@redhat.com
Cc: hpa@zytor.com
Cc: x86@kernel.org
Cc: thomas.lendacky@amd.com
Cc: helgaas@kernel.org
Cc: linux-pci@vger.kernel.org
Link: https://lkml.kernel.org/r/5f8877bd413f2ea0833378dd5454df0720e1c0df.1537885177.git.puwen@hygon.cn