flexfax: Class 2[.0] Receive Trigger 021 or 022

[David Woolley <david@djwhome.demon.co.uk>]

The following from the source code seems rather relevant to the
two current problems where there is a possibility that the wrong
receive trigger is being sent:

    /*
     * Define the code to send to the modem to trigger the
     * transfer of received Phase C data to the host.  Most
     * modems based on SP-2388-A (Class 2) use DC1 while those
     * based on SP-2388-B (Class 2.0) use DC2.  There are some
     * exceptions (ZyXEL and modems based on Rockwell RC32ACL
     * parts), but they are expected to set the appropriate
     * value in the config file.
     */

Many generic modems are Rockwell based but class 2, not 2.0.

I may have been a little misled by the supplied config files as these
probably let the \021 case default and only specify a value for 
exception cases.

Note DC1 = \021 and DC2 = \022.