seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g

__SEQ_LOCKDEP() is an expression gate for the
seqcount_LOCKNAME_t::lock member. Rename it to be about the member,
not the gate condition.

Later (PREEMPT_RT) patches will make the member available for !LOCKDEP
configs.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>