Revert "Allow FDE references outside the +/-2GB range supported by PC relative offsets for code models other than small/medium. For JIT application, memory layout is less controlled and can result in truncations otherwise."

This reverts commit r222538.

It's causing test failures for CFI, at least on Darwin:

http://lab.llvm.org:8080/green/job/clang-stage1-cmake-RA-incremental/1189/
http://lab.llvm.org:8080/green/job/clang-stage1-configure-RA_check/1391/

Note that the previous incremental build was on r222537, and the CFI
tests weren't failing:
http://lab.llvm.org:8080/green/job/clang-stage1-cmake-RA-incremental/1188/