kernel: enable pressure interface

kernel: enable pressure interface

PSI provides a canonical way to see resource pressure increases as
they develop, with pressure metrics for three major resources:
memory, CPU, and IO. PSI stats are like barometers that provide
fair warning of impending resource shortages, enabling users to
take more proactive, granular, and nuanced steps when resources
start becoming scarce.

References:
* https://www.kernel.org/doc/html/latest/accounting/psi.html
* https://lwn.net/Articles/759781/

Build system: x86/64
Build-tested: x86/64/AMD Cezanne, flogic/glinet_gl-mt6000
Run-tested: x86/64/AMD Cezanne, flogic/glinet_gl-mt6000

Signed-off-by: John Audia <therealgraysky@proton.me>
Link: https://github.com/openwrt/openwrt/pull/13819
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>