ARC: Improve identification of ARC cores

ARC: Improve identification of ARC cores

1. Try to guess a ARC core template that was used
   i.e. not just name a core family but something more
   menaingful like "ARC HS38", "ARC EM11D" etc.

   We do it checking availability of the key differentiation
   features like:
    - Caches (we actually only check for L1 I$ fpr simplicity)
    - XY-memory
    - DSP extensions etc.

2. Identify ARC subsystems

3. Print core clock frequency

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>