[X86] Pre-size some SmallVectors using the constructor in the shuffle lowering code instead of using push_back. Some of these already did this but used resize or assign instead of the constructor. NFC

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272872 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed