Bluetooth: Enter active mode before establishing a SCO link.
When in sniff mode with a long interval time (1.28s) it can take 4+ seconds
to establish a SCO link. Fix by requesting active mode before requesting
SCO connection. This improves SCO setup time to ~500ms.
Bluetooth headsets that use a long interval time, and exhibit the long
SCO connection time include Motorola H790, HX1 and H17. They have a
CSR 2.1 chipset.
Verified this behavior and fix with host Bluetooth chipsets: BCM4329 and
TI1271.