Bluetooth: Remove redundant check for remote_key_dist

In the smp_cmd_sign_info() function the SMP_DIST_SIGN bit is explicitly
cleared early on in the function. This means that there's no need to
check for it again before calling smp_distribute_keys().

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