[AArch64][InstCombine] Fold MLOAD and zero extensions into MLOAD

Accord the discussion in D122281, we missing an ISD::AND combine for MLOAD
because it relies on BuildVectorSDNode is fails for scalable vectors.
This patch is intend to handle that, so we can circle back the type MVT::nxv2i32

Reviewed By: paulwalker-arm

Differential Revision: https://reviews.llvm.org/D122703