Previously asymptomatic because high 32 bits were zero.

Fixes: 96c211f1 ("drm/amdkfd: Relocate TBA/TMA to opposite side of VM hole")
Signed-off-by: Jay Cornwall <jay.cornwall@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>