drm/i915: Stop setting SNB min-freq-table 0 on powersave setup

The min-freq-table is an array of values that match each CPU frequency to
an equivalent GPU frequency. Setting a single value of 0 on init is both
illegal (generates an error from the PCU) and nonsensical. Let's see if
we survive without that error.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20161021205531.8651-1-chris@chris-wilson.co.uk
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>