drm/amd/amdgpu: Widen mmio trace register address width

Support wider address spaces, make it 32-bit so we don't have to
revisit this for a while.

Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>