drm/amdgpu: Increase PSP runtime TMR region size

Aldebaran uses more than 4M runtime TMR. The current
hard coded 4M TMR is not big enough for Aldebaran.
Increase it to 8M.

v2: Only do 8M size for ALDEBARAN (Hawking)

Signed-off-by: Oak Zeng <Oak.Zeng@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>