Improve debug messages and removed DSP references from MMU FW code

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>