The CIA_{GET,SET} macros serve the same function as CPU_PC_{GET,SET}
except the latter adds a layer of indirection via the sim state. This
lets models set up different functions at runtime and doesn't reach so
directly into the arch-specific cpu state.
It also doesn't make sense to have two sets of macros that do exactly
the same thing, so lets standardize on the one that gets us more.
Now that all the targets are utilizing CPU_PC_{FETCH,STORE}, and the
cpu state is multicore, and the STATE_CPU defines match, we can move
it all to the common code.
