MAJOR: muxes: No longer use app_ops .wake() callback function from muxes

MAJOR: muxes: No longer use app_ops .wake() callback function from muxes

Thanks to previous commits, it is now possible to wake the data layer up,
via a tasklet_wakeup, instead of using the app_ops .wake() callback
function.

When a data layer must be notified of a mux event (an error for instance),
we now always perform a tasklet_wakeup(). TASK_WOKEN_MSG state is used by
default. TASK_WOKEN_IO is eventually added if the data layer was subscribed
to receives or sends.

Changes are not trivial at all. We replaced a synchronous call to the
sc_conn_process() function by a tasklet_wakeup().