Bluetooth: Merge L2CAP and SCO modules into bluetooth.ko

Actually doesn't make sense have these modules built separately.
The L2CAP layer is needed by almost all Bluetooth protocols and profiles.
There isn't any real use case without having L2CAP loaded.
SCO is only essential for Audio transfers, but it is so small that we can
have it loaded always in bluetooth.ko without problems.
If you really doesn't want it you can disable SCO in the kernel config.

Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>