sys-kernel/coreos-modules: enable PSI (Pressure Stall Information)

Enable Kernel config for PSI (Pressure Stall Information), which might
help system administrators to detect bottleneck in cpu, memory and io
in an easy way.

```
$ zgrep -i _psi /proc/config.gz
CONFIG_PSI=y

$ ls -l /proc/pressure/
-r--r--r--. 1 root root 0 Oct  7 11:56 cpu
-r--r--r--. 1 root root 0 Oct  7 11:56 io
-r--r--r--. 1 root root 0 Oct  7 11:56 memory
$ cat /proc/pressure/cpu
some avg10=0.13 avg60=0.68 avg300=0.28 total=1195993
$ cat /proc/pressure/io
some avg10=0.00 avg60=1.11 avg300=0.68 total=2828208
full avg10=0.00 avg60=0.91 avg300=0.56 total=2334731
$ cat /proc/pressure/memory
some avg10=0.00 avg60=0.00 avg300=0.00 total=0
full avg10=0.00 avg60=0.00 avg300=0.00 total=0
```

See also https://www.kernel.org/doc/html/latest/accounting/psi.html ,
https://facebookmicrosites.github.io/psi/docs/overview

Fixes https://github.com/flatcar-linux/Flatcar/issues/162

sdk_container/src/third_party/coreos-overlay/sys-kernel/coreos-modules/files/commonconfig-5.9

@@ -726,6 +726,8 @@ CONFIG_PRINTK_TIME=y
 # CONFIG_PRINT_QUOTA_WARNING is not set
 CONFIG_PROC_KCORE=y
 CONFIG_PROFILING=y
+CONFIG_PSI=y
+# CONFIG_PSI_DEFAULT_DISABLED is not set
 CONFIG_QED=m
 CONFIG_QEDE=m
 CONFIG_QEDF=m