Revert "Bluetooth: Add option for disabling legacy ioctl interfaces"

This reverts commit dbbccdc4

.

It turns out that the "legacy" users aren't so legacy at all, and that
turning off the legacy ioctl will break the current Qt bluetooth stack
for bluetooth LE devices that were released just a couple of months ago.

So it's simply not true that this was a legacy interface that hasn't
been needed and is only limited to old legacy BT devices.  Because I
actually read Kconfig help messages, and actively try to turn off
features that I don't need, I turned the option off.

Then I spent _way_ too much time debugging BLE issues until I realized
that it wasn't the Qt and subsurface development that had broken one of
my dive computer BLE downloads, but simply my broken kernel config.

Maybe in a decade it will be true that this is a legacy interface.  And
maybe with a better help-text and correct dependencies, this kind of
legacy removal might be acceptable.  But as things are right now both
the commit message and the Kconfig help text were misleading, and the
Kconfig option had the wrong dependenencies.

There's no reason to keep that broken Kconfig option in the tree.

Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>