drm/amdgpu: remove unused TRACE_SYSTEM_STRING define

Port of 77cb2fea1e to
amdgpu.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Alex Deucher 2015-05-21 02:24:48 -04:00
commit 15a16ff606