drm/amdgpu: Fix ras debugfs data parse

Unzero char is accepted by sscanf, so when data is structure but
unexpectedly return error invalid;

Signed-off-by: xinhui pan <xinhui.pan@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>