PM / sleep: add TEST_PLATFORM support for freeze state

Invoke freeze_enter() after suspend_test(TEST_PLATFORM) being invoked.

So when setting /sys/power/pm_test to "platform", it can be used to
check if freeze state is working well after all devices are suspended
and before processors are blocked,

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

kernel/power/suspend.c

@@ -184,6 +184,9 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
 			goto Platform_wake;
 	}
 
+	if (suspend_test(TEST_PLATFORM))
+		goto Platform_wake;
+
 	/*
 	 * PM_SUSPEND_FREEZE equals
 	 * frozen processes + suspended devices + idle processors.
@@ -195,9 +198,6 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
 		goto Platform_wake;
 	}
 
-	if (suspend_test(TEST_PLATFORM))
-		goto Platform_wake;
-
 	error = disable_nonboot_cpus();
 	if (error || suspend_test(TEST_CPUS))
 		goto Enable_cpus;