Bluetooth: Move {min,max}_key_size debugfs into hci_debugfs_create_le

The debugfs entries for {min,max}_key_size are created during SMP
registration and thus it might lead to multiple attempts to create the
same entries. Avoid this by moving them to the LE controller init
section.

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