[AArch64] Fix i64 nontemporal high-half extraction.

[AArch64] Fix i64 nontemporal high-half extraction.

Since we only have pair - not single - nontemporal store instructions,
we have to extract the high part into a separate register to be able
to use them.

When the initial nontemporal codegen support was added, I wrote the
extract using the nonsensical UBFX [0,32[.
Use the correct LSR form instead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@259134 91177308-0d34-0410-b5e6-96231b3b80d8