match unknown ATI display devices as amdgpu in fw_update

match unknown ATI display devices as amdgpu in fw_update

For recent devices amdgpu matches via the hardware ip discovery table,
not with a table of pci vendor and product ids.

So amdgpu_devlist.h and pcidevs do not cover all devices that amdgpu
may match.

in dmesg amdgpu with an unknown product takes the form:

ramdisk kernel, bios/mbr:
vga1 at pci12 dev 0 function 0 vendor "ATI", unknown product 0x687f rev 0xc3

ramdisk kernel, efi or non-x86 arch:
vendor "ATI", unknown product 0x687f (class display subclass VGA, rev 0x03) at pci12 dev 0 function 0 not configured

non-ramdisk kernel:
amdgpu0 at pci12 dev 0 function 0 vendor "ATI", unknown product 0x687f rev 0xc3

ok deraadt@ on an earlier version