Bluetooth: Fix scope of sc_only_mode debugfs entry

The sc_only_mode debugfs entry is used to read the current state of the
Secure Connections Only mode. Before Bluetooth 4.2 this mode was only
for BR/EDR controllers and with that tight to the support Secure Simple
Pairing. Since Secure Connections is now available for BR/EDR and LE
this debugfs entry is no longer correctly place.

Move it to the common section and enable it when either BR/EDR Secure
Connections feature is supported or when the controller has LE support.

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