drm/amdgpu: attempt xgmi perfmon re-arm on failed arm

The DF routines to arm xGMI performance will attempt to re-arm both on
performance monitoring start and read on initial failure to arm.

Signed-off-by: Jonathan Kim <Jonathan.Kim@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>