Remove isProfitableToDuplicateIndirectBranch target hook. It is profitable

Remove isProfitableToDuplicateIndirectBranch target hook.  It is profitable
for all the processors where I have tried it, and even when it might not help
performance, the cost is quite low.  The opportunities for duplicating
indirect branches are limited by other factors so code size does not change
much due to tail duplicating indirect branches aggressively.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90144 91177308-0d34-0410-b5e6-96231b3b80d8