rtnr: reject out-of-range control switch element counts

The SWITCH control get and set handlers looped over a host-supplied
element count while reading/writing the control channel array, which
could run past the IPC payload. Reject counts larger than the maximum
channel count in both handlers before the loop.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Author: lrgirdwo