[X86] Rename combineVSZext->combineExtendVectorInreg. NFC

Now that we no longer have target specific vector extend nodes let's make the function name match the nodes we do use.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@347268 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed