locking/static_key: always define static_branch_deferred_inc

This interface is currently only defined if CONFIG_JUMP_LABEL. Make it
available also when jump labels are off.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>