vmlinux: Avoid weak reference to notes section

Weak references are references that are permitted to remain unsatisfied
in the final link. This means they cannot be implemented using place
relative relocations, resulting in GOT entries when using position
independent code generation.

The notes section should always exist, so the weak annotations can be
omitted.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>