drm/amdgpu: add the accelerator PCIe class

Add the accelerator PCIe class and match the
class in amdgpu for 0x1002 devices of that class.

From PCI spec:
"PCI Code and ID Assignment, r1.9, sec 1, 1.19"

Signed-off-by: Shiwu Zhang <shiwu.zhang@amd.com>
Acked-by: Lijo Lazar <lijo.lazar@amd.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>  # pci_ids.h
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>