mm/damon/sysfs: use dynamically allocated repeat mode damon_call_control

DAMON sysfs interface is using a single global repeat mode
damon_call_control variable for refresh_ms handling, for all DAMON
contexts.  As a result, when there are more than one context, the single
global damon_call_control is unexpectedly over-written (corrupted). 
Particularly the ->link field is overwritten by the multiple contexts and
this can cause a user hangup, and/or a kernel crash.  Fix it by using
dynamically allocated damon_call_control object per DAMON context.

Link: https://lkml.kernel.org/r/20250908201513.60802-3-sj@kernel.org
Link: https://lore.kernel.org/20250904011738.930-1-yunjeong.mun@sk.com [1]
Link: https://lore.kernel.org/20250905035411.39501-1-sj@kernel.org

 [2]
Fixes: d809a7c6 ("mm/damon/sysfs: implement refresh_ms file internal work")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Yunjeong Mun <yunjeong.mun@sk.com>
Closes: https://lore.kernel.org/20250904011738.930-1-yunjeong.mun@sk.com


Signed-off-by: Andrew Morton <akpm@linux-foundation.org>