SPA_POD_CHOICE_ENUM_Int must always take at least 2 values as first one
is default. (Just 1 value no longer works on current master, and it's
anyway incorrect.)
Replace with just SPA_POD_Int, as there's just one choice.
Don't try to write data in too large blocks.
This controls the maximum amount of data to send at once. sco-io will
buffer and fragment packets to the right size.
Previously in sco-sink, SO_SNDBUF was not set, so there could be a
longer queue in the socket.
