clang: remove obsolete patch

clang: remove obsolete patch

This musl-related fix to TargetLibraryInfo has been obsolete since LLVM
version 5.0 as it was fixed in a different way:

commit d21529fa0df71327aab230786e345b2071f4ac4f
Author: David L. Jones <dlj@google.com>
Date:   Mon Jan 23 23:16:46 2017 +0000

    [Analysis] Add LibFunc_ prefix to enums in TargetLibraryInfo. (NFC)

    Summary:
    The LibFunc::Func enum holds enumerators named for libc functions.
    Unfortunately, there are real situations, including libc implementations, where
    function names are actually macros (musl uses "#define fopen64 fopen", for
    example; any other transitively visible macro would have similar effects).

    Strictly speaking, a conforming C++ Standard Library should provide any such
    macros as functions instead (via <cstdio>). However, there are some "library"
    functions which are not part of the standard, and thus not subject to this
    rule (fopen64, for example). So, in order to be both portable and consistent,
    the enum should not use the bare function names.

    The old enum naming used a namespace LibFunc and an enum Func, with bare
    enumerators. This patch changes LibFunc to be an enum with enumerators prefixed
    with "LibFFunc_". (Unfortunately, a scoped enum is not sufficient to override
    macros.)

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>