Revert "Bluetooth: validate BLE connection interval updates"

This reverts commit c49a8682.

There are devices which require low connection intervals for usable operation
including keyboards and mice. Forcing a static connection interval for
these types of devices has an impact in latency and causes a regression.

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