Remove a (what appears to be) overly strict assertion. Here is what happened:

Remove a (what appears to be) overly strict assertion. Here is what happened:
1. ppcf128 select is expanded to f64 select's.
2. f64 select operand 0 is an i1 truncate, it's promoted to i32 zero_extend.
3. f64 select is updated. It's changed back to a "NewNode" and being re-analyzed.
4. f64 select operands are being processed. Operand 0 is a "NewNode". It's being expunged out of ReplacedValues map.
5. ExpungeNode tries to remap f64 select and notice it's a "NewNode" and assert.
Duncan, please take a look. Thanks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60443 91177308-0d34-0410-b5e6-96231b3b80d8