Bluetooth: Expose inquiry_cache debugfs only on BR/EDR controllers

The inquiry_cache debugfs entry is only valid for BR/EDR capable
controllers. In case of single mode LE-only controllers that
entry is not valid.

Move the creating of the debugfs entries to the end of controller
init and only create the inquiry_cache entry if BR/EDR is actually
supported.

At the same time this avoids creating any debugfs entries for
AMP controllers since none of the entries are valid there.

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