drm/amdgpu: bypass tmr when reserve c2p memory

C2P memory reserved should not in tmr memory range.

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>