ARC: Kconfig: rename CPU_ARCV2 option to ISA_ARCV2

* Rename CPU_ARCV2 to ISA_ARCV2. That helps to avoid conflict between
  CPU families naming and ISAs naming and aligns this options
  with other ARC OSS projects.

* Generalize ARCV2 check to ARC check where it is required.

NOTE: we add ISA_ARCV2 option in a choice list as a preparation
for ISA_ARCV3 addition.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
9 files changed