Bluetooth: Restrict application of socket options

The new socket options should only be evaluated for SOL_BLUETOOTH level
and not for every other level. Previously this causes some minor issues
when detecting if a kernel with certain features is available.

Also restrict BT_SECURITY to SOCK_SEQPACKET for L2CAP and SOCK_STREAM for
the RFCOMM protocol.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>