drm/amdgpu: add function to check tmz capability (v4)

Add a function to check tmz capability with kernel parameter and ASIC type.

v2: use a per device tmz variable instead of global amdgpu_tmz.
v3: refine the comments for the function. (Luben)
v4: add amdgpu_tmz.c/h for future use.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>