Improve debug messages and removed DSP references from MMU FW code

 As the code is expected to work with another mmu other than DSP mmu; "DSP"
string was removed from the code in the following situations:

- Debug messages
- Local variables name
- Comments

 Another improvement is done for debug messages. The MMU name is printed
in debug messages.

Signed-off-by: Eduardo Valentin <eduardo.valentin@indt.org.br>
Signed-off-by: Tony Lindgren <tony@atomide.com>