[Upstream port] Create and initialize arcv2-target and arc32-arch structures

[EvgeniiDidin]

Every architecture has a structure, where specific details are described. This structure on initialize step is passing to openocd target instance.

Each architecture in openocd has its own structure called _target, where standard handlers are described.

[EvgeniiDidin]

Resolving issue commits:
d062051
5e3834e

By the fact we are having only 32-bit arc processors, I decided to replace "arc32" prefix wirh "arc".