powerpc/jump_label: use HAVE_JUMP_LABEL?

CONFIG_JUMP_LABEL doesn't ensure HAVE_JUMP_LABEL, if it
is not the case use maintainers's own mutex to guard
the modification of global values.

Signed-off-by: Zhouyi Zhou <yizhouzhou@ict.ac.cn>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>