[title]
Check for CHPIDs that are not available

[description]
Unavailable CHPIDs can cause I/O stalls and errors and might result in required
I/O devices that are not visible within Linux. This check analyzes sysfs
status information to identify CHPIDs that are unavailable because of a
"configure standby" or a "vary offline" operation. These operations are commonly
performed as part of hardware maintenance procedures and need to be reverted
after maintenance has finished.
