Add support for version 4 of the DPFE API. This new version is largely
identical to version 3. The main difference is that all commands now
take the MHS version number as the first argument. Any other arguments
have been pushed down by one (i.e. what used to be arg0 in v3 is arg1 in
v4).
Signed-off-by: Markus Mayer <mmayer@xxxxxxxxxxxx>