Bluetooth: Fix validating IO capability values in mgmt commands

The valid range of IO capabilities for the Set IO Capability and Pair
Device mgmt commands is 0-4 (4 being the KeyboarDisplay capability for
SMP). We should return an invalid parameters error if user space gives
us a value outside of this range.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>