drm/amdgpu: refine PSP TA firmware info print in debugfs

refine PSP TA firmware info print in amdgpu_firmware_info().

Signed-off-by: Kevin Wang <kevin1.wang@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>