drm/i915/selftests: Downgrade severity of CS/SRM frequency scaling tests

drm/i915/selftests: Downgrade severity of CS/SRM frequency scaling tests

Gracefully skip over the failures in the frequency scaling for the
moment, the results are under review.

References: https://gitlab.freedesktop.org/drm/intel/-/issues/1754
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: "Sundaresan, Sujaritha" <sujaritha.sundaresan@intel.com>
Cc: "Ewins, Jon" <jon.ewins@intel.com>
Reviewed-by: Sujaritha Sundaresan <sujaritha.sundaresan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200723153805.8076-1-chris@chris-wilson.co.uk
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>