[AArch64] add tests for fmul x, -2.0 with undef elts; NFC

Also, add tests with commuted operands. There was no coverage for that case.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@344531 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed