mm/damon/core: do damos walking in entire regions granularity

mm/damon/core: do damos walking in entire regions granularity

damos_walk_control can be installed while DAMOS is walking the regions.
This means the walk callback function invocations can be started from a
region at the middle of the regions list.  This makes it hard to be used
reliably.  Particularly, DAMOS tried regions update for collecting
monitoring results gets problematic results.  Increase the
walk_control_lock critical section to do walking in entire regions
granularity.

Link: https://lkml.kernel.org/r/20250210182737.134994-4-sj@kernel.org
Fixes: bf0eaba0ff9c ("mm/damon/core: implement damos_walk()")
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>