Fix really stupid ARM EHABI info generation bug: we should not emit

eh table and handler data if there are no landing pads in the function.
Patch by Logan Chien with some cleanups from me.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167945 91177308-0d34-0410-b5e6-96231b3b80d8