Fix possible coherency issues between PEs related to I-cache

[wma_semihalf.com]

Summary

Basing on B.2.3.4:
Synchronization and coherency issues between data and
instruction accesses.

To ensure that modified instructions are visible to all PEs
in a shareability domain one need to perform following sequence:
1. Clean D-cache
2. Ensure the visibility of data cleaned from cache
3. Invalidate I-cache
4. Ensure completion
5. In SMP system PE must issue isb to ensure execution of the
   modified instructions