neuron: ch_haven: Move msgq init to sync thread

The neuron channels may init and probe before the secondary vm is
loaded and the resources queried from resource manager. This results
in either a blocking call or EAGAIN returned when sending a doorbell.

Move the msgq_init call from the probe to the channel sync thread. This
will ensure the init thread can continue if the doorbell send api needs
to block or busywait loop.

Change-Id: I0f5562968d59a3dc0a361aca9e4e60ffebcb70be
Signed-off-by: Chris Lew <clew@codeaurora.org>