target-*/exec.h cleanup

This patch gets rid of target-*/exec.h headers by moving the corresponding
definitions either inside target-*/op_helper.c, or dyngen-exec.h for the
global register-based 'env' value, which will be removed in future patches.

Upstream 3e4571724fb92c77de81d8b54957de8232be6706

Change-Id: I513d5c27c01c6dc727c1ce6fb7f3a7a5dc03800f
14 files changed