[SelectionDAG] Use WidenTargetBoolean in WidenVecRes_MLOAD and WidenVecOp_MSTORE...

[SelectionDAG] Use WidenTargetBoolean in WidenVecRes_MLOAD and WidenVecOp_MSTORE instead of implementing it manually and incorrectly.

The CONCAT_VECTORS operand get its type from getSetCCResultType, but if the mask type and the setcc have different scalar sizes this creates an illegal CONCAT_VECTORS operation. The concat type should be 2x the mask type, and then an extend should be added if needed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@319744 91177308-0d34-0410-b5e6-96231b3b80d8