powerpc: Prefer __section and __printf from compiler_attributes.h

Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
[mpe: Drop changes to a/p/boot which doesn't use linux headers]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190812215052.71840-10-ndesaulniers@google.com