[AArch64] ACLE: Fix issue for mismatching enum types with builtins.

This patch fixes an issue with the SVE prefetch and qinc/qdec intrinsics
that take an `enum` argument, but where the builtin prototype encodes
these as `int`. Some code in SemaDecl found the mismatch and chose
to forget about the builtin altogether, which meant that any future
code using that builtin would fail. The code that forgets about the
builtin was actually obsolete after D77491 and should have been removed.
This patch now removes that code.

This patch also fixes another issue with the SVE prefetch intrinsic
when built with C++, where the builtin didn't accept the correct
pointer type, which should be `const void *`.

Reviewed By: tambre

Differential Revision: https://reviews.llvm.org/D100046