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

Arithmetic 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@222272 91177308-0d34-0410-b5e6-96231b3b80d8