jump_label: Refactor #ifdef of struct static_key

Move #ifdef CONFIG_JUMP_LABEL inside the struct static_key.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220213165717.2354046-2-masahiroy@kernel.org