sched/psi: Select KERNFS as needed

mainline inclusion
from mainline-v6.6-rc1
commit 98dfdd9e
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7DHPO

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=98dfdd9ee93995a408192dbbf3dd219ba23e3738



-------------------------------------------------

Users of KERNFS should select it to enforce its being built, so
do this to prevent a build error.

In file included from ../kernel/sched/build_utility.c:97:
../kernel/sched/psi.c: In function 'psi_trigger_poll':
../kernel/sched/psi.c:1479:17: error: implicit declaration of function 'kernfs_generic_poll' [-Werror=implicit-function-declaration]
 1479 |                 kernfs_generic_poll(t->of, wait);

Fixes: aff03707 ("sched/psi: use kernfs polling functions for PSI trigger polling")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Link: lore.kernel.org/r/202307310732.r65EQFY0-lkp@intel.com
Signed-off-by: Lu Jialin <lujialin4@huawei.com>