mm/damon: add 'allow' argument to damos_new_filter()

DAMON API users should set damos_filter->allow manually to use a DAMOS
allow-filter, since damos_new_filter() unsets the field always.  It is
cumbersome and easy to mistake.  Add an arugment for setting the field to
damos_new_filter().

Link: https://lkml.kernel.org/r/20250109175126.57878-6-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>