amdgpu: A new option to choose which device to run most tests

This can be used to test multiple GPUs

v2: Use PCI bus ID and optional PCI device ID to choose device
    Add an option to display information of AMDGPU devices

Tested:
   ./amdgpu_test -p
   ./amdgpu_test
   ./amdgpu_test -b 1 #fail as expected
   ./amdgpu_test -b 6 #pass
   ./amdgpu_test -b -d 1 #fail as expected
   ./amdgpu_test -b -d 0 #pass

Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Alex Xie <AlexBin.Xie@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>