Refactor DSP init routines so there is a dedicated init function
for the stages that need it. Remove the DSP_INIT configure message.
This allows the init code to be safely marked INIT_ATTR, saving a
bit of code size, and allowing the linker to verify that there are
no unsafe references to the init routines.
Change-Id: I1702f0f579bbb300a6fe7d0e67b13aa2e9dd7f8a
