Bluetooth: MGMT: Fix misplaced BT_HS check

The upstream commit b560a208cda0 ("Bluetooth: MGMT: Fix not checking if
BT_HS is enabled") inserted a new check in the `set_hs` function.
However, its backported version in stable (commit 5abe9f99f512
("Bluetooth: MGMT: Fix not checking if BT_HS is enabled")),
added the check in `set_link_security` instead.

This patch restores the intent of the upstream commit by moving back the
BT_HS check to `set_hs`.

Fixes: 5abe9f99f512 ("Bluetooth: MGMT: Fix not checking if BT_HS is enabled")
Signed-off-by: Guillaume Bertholon <guillaume.bertholon@ens.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>