[FastISel][AArch64] Refactor code to use isTypeSupported. NFC.

Gets rid of isLoadStoreTypeLegal and replace it with isTypeSupported.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217826 91177308-0d34-0410-b5e6-96231b3b80d8
[FastISel][AArch64] Refactor selectAddSub, selectLogicalOp, and SelectShift. NFC.

Small refactor to tidy up the code a little.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217827 91177308-0d34-0410-b5e6-96231b3b80d8