[X86] Remove part of an if condition that should always be true.

The IndexReg will always be non-null at this point. Earlier in the function, if
IndexReg was null we set it to CurDAG->getRegister(0, VT) which made it
non-null.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359170 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed