samples/bpf: Add a workaround for asm_inline

This was added in commit eb111869 ("compiler-types.h: add asm_inline
definition") and breaks samples/bpf as clang does not support asm __inline.

Fixes: eb111869

 ("compiler-types.h: add asm_inline definition")
Co-developed-by: Florent Revest <revest@google.com>
Signed-off-by: Florent Revest <revest@google.com>
Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191002191652.11432-1-kpsingh@chromium.org