drm/amdgpu/swsmu: clean up unused header in swsmu

clean up unused header in swsmu driver stack:
1. pp_debug.h
2. amd_pcie.h
3. soc15_common.h

Signed-off-by: Kevin Wang <kevin1.wang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>