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

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

This should fix a bug found by Chad.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218275 91177308-0d34-0410-b5e6-96231b3b80d8