intel_idle: improve C-state flags handling robustness

JIRA: https://issues.redhat.com/browse/RHEL-11351



commit 00433eae
Author: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Date:   Wed Apr 19 17:39:44 2023 +0300

    intel_idle: improve C-state flags handling robustness

    The following C-state flags are currently mutually-exclusive and should not
    be combined:
      * IRQ_ENABLE
      * IBRS
      * XSTATE

    There is a warning for the situation when the IRQ_ENABLE flag
    is combined with the IBRS flag, but no warnings for other combinations.
    This is inconsistent and prone to errors.

    Improve the situation by adding warnings for all the unexpected
    combinations. Add a couple of helpful commentaries too.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Reviewed-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Signed-off-by: David Arcari <darcari@redhat.com>