Bluetooth: Change scope of the enable_hs module parameter

This variable is currently only accessible within l2cap_core.c, but
it is also needed in l2cap_sock.c

Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Acked-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>