kswapd: replace try_to_freeze() with kthread_freezable_should_stop()

Instead of using try_to_freeze, use kthread_freezable_should_stop in
kswapd.  By this, we can avoid unnecessary freezing when kswapd should
stop.

Link: https://lkml.kernel.org/r/20240126152556.58791-1-ppbuk5246@gmail.com


Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>