Bluetooth: btintel: Fix incorrect out of memory check

Currently *ven_data is being assigned the return from a kmalloc call but
the out-of-memory check is checking ven_data and not *ven_data. Fix this
by adding the missing dereference * operator,

Addresses-Coverity: ("Dereference null return")
Fixes: 70dd9789 ("Bluetooth: btintel: Define a callback to fetch codec config data")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>