Revert "PM: sleep: Do not assume that "mem" is always present"

Revert commit bfcc1e67 ("PM: sleep: Do not assume that "mem" is
always present"), because it breaks compatibility with user space
utilities assuming that "mem" will always be present in
/sys/power/state.

Fixes: bfcc1e67 ("PM: sleep: Do not assume that "mem" is always present")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

kernel/power/suspend.c

@@ -171,7 +171,8 @@ static bool valid_state(suspend_state_t state)
 
 void __init pm_states_init(void)
 {
-	/* "freeze" is always present in /sys/power/state. */
+	/* "mem" and "freeze" are always present in /sys/power/state. */
+	pm_states[PM_SUSPEND_MEM] = pm_labels[PM_SUSPEND_MEM];
 	pm_states[PM_SUSPEND_TO_IDLE] = pm_labels[PM_SUSPEND_TO_IDLE];
 	/*
 	 * Suspend-to-idle should be supported even without any suspend_ops,
@@ -213,7 +214,6 @@ void suspend_set_ops(const struct platform_suspend_ops *ops)
 	}
 	if (valid_state(PM_SUSPEND_MEM)) {
 		mem_sleep_states[PM_SUSPEND_MEM] = mem_sleep_labels[PM_SUSPEND_MEM];
-		pm_states[PM_SUSPEND_MEM] = pm_labels[PM_SUSPEND_MEM];
 		if (mem_sleep_default >= PM_SUSPEND_MEM)
 			mem_sleep_current = PM_SUSPEND_MEM;
 	}