atomisp: clean up the hmm init/cleanup indirections

We don't need any of these indirections as we only support one MMU type. Start
by getting rid of the init/clear/free ones. The init ordering check we already
pushed down in a previous patch.

The allocation side is more complicated so leave it for now.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>