drm/amdgpu: Adjust TMR address alignment as per HW requirement

According to HW engineer, they prefer the TMR address be "naturally aligned", e.g. the start address
must be an integer divide of TME size.

Signed-off-by: shaoyunl <shaoyun.liu@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>