Revert mm/vmstat.c: fix vmstat_update() preemption BUG

Upstream commit 28557cc106e6d2aa8b8c5c7687ea9f8055ff3911

The commit c7f26ccfb2c3 ("mm/vmstat.c: fix vmstat_update() preemption BUG") does not fix a bug but papers over it. The reported and author never came back with an explanation nor was the symptom reproduced by someone else. The commit was reverted upstream but it made its was to the stable tree therefore I ask there for a revert, too.

Please include this patch in the v4.14 stable tree.

Sebastian