seqlock: kernel-doc: Specify when preemption is automatically altered

The kernel-doc annotations for sequence counters write side functions
are incomplete: they do not specify when preemption is automatically
disabled and re-enabled.

This has confused a number of call-site developers. Fix it.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/CAHk-=wikhGExmprXgaW+MVXG1zsGpztBbVwOb23vetk41EtTBQ@mail.gmail.com