mm/damon/stat: remove __read_mostly from memory_idle_ms_percentiles

mm/damon/stat: remove __read_mostly from memory_idle_ms_percentiles

The 'memory_idle_ms_percentiles' array in DAMON_STAT is updated frequently
by the kernel to reflect the latest idle time statistics.  Marking it as
'__read_mostly' is inappropriate for data that is regularly written to, as
it can lead to cache pollution in the read-mostly section.

Remove the '__read_mostly' annotation to accurately reflect the
variable's usage pattern.

Link: https://lkml.kernel.org/r/20260130085603.1814-1-lirongqing@baidu.com
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>