[FastISel][AArch64] Also allow folding of sign-/zero-extend and logical
shift-right for booleans (i1).

Logical shift-right immediate with sign-/zero-extensions also works for boolean
values.  Update the assert and the test cases to reflect that fact.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222270 91177308-0d34-0410-b5e6-96231b3b80d8