Revert "x86/asm: Allow again using asm.h when building for the 'bpf' clang target"

Revert "x86/asm: Allow again using asm.h when building for the 'bpf' clang target"

This reverts commit ca26cffa4e4aaeb09bb9e308f95c7835cb149248.

Newer clang versions accept that asm(_ASM_SP) construct, and now that
the bpf-script-test-kbuild.c script, used in one of the 'perf test LLVM'
subtests doesn't include ptrace.h, which ended up including
arch/x86/include/asm/asm.h, we can revert this patch.

Suggested-by: Yonghong Song <yhs@fb.com>
Link: https://lkml.kernel.org/r/613f0a0d-c433-8f4d-dcc1-c9889deae39e@fb.com
Acked-by: Yonghong Song <yhs@fb.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-nqozcv8loq40tkqpfw997993@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>