mm/damon/sysfs: remove damon_sysfs_cmd_request code from damon_sysfs_handle_cmd()

mm/damon/sysfs: remove damon_sysfs_cmd_request code from damon_sysfs_handle_cmd()

damon_sysfs_handle_cmd() handles user requests that it can directly handle
on its own.  For requests that need to be handled from damon_callback
hooks, it uses DAMON sysfs interface's own synchronous damon_callback
hooks management mechanism, namely damon_sysfs_cmd_request.  Now all user
requests are handled without damon_callback hooks, so
damon_sysfs_cmd_request client code in damon_sysfs_andle_cmd() does
nothing in real.  Remove the unnecessary code.

Link: https://lkml.kernel.org/r/20250306175908.66300-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>