intel_idle: close avn_cstates array with correct marker

Close avn_cstates array with correct marker to avoid overflow
in function intel_idle_cpu_init().

[rjw: The problem was introduced when commit 22e580d0 was merged
 on top of eba682a5 (intel_idle: shrink states tables).]

Fixes: 22e580d0 (intel_idle: Fixed C6 state on Avoton/Rangeley processors)
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>