tracing: allow tracing of suspend/resume & hibernation code again

Impact: widen function-tracing to suspend+resume (and hibernation) sequences

Now that the ftrace kernel thread is gone, we can allow tracing
during suspend/resume again.

So revert these two commits:

  f42ac38c5 "ftrace: disable tracing for suspend to ram"
  41108eb10 "ftrace: disable tracing for hibernation"

This should be tested very carefully, as it could interact with
altneratives instruction patching, etc.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/power/main.c b/kernel/power/main.c
index b8f7ce9..613f169 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -22,7 +22,6 @@
 #include <linux/freezer.h>
 #include <linux/vmstat.h>
 #include <linux/syscalls.h>
-#include <linux/ftrace.h>
 
 #include "power.h"
 
@@ -317,7 +316,7 @@
  */
 int suspend_devices_and_enter(suspend_state_t state)
 {
-	int error, ftrace_save;
+	int error;
 
 	if (!suspend_ops)
 		return -ENOSYS;
@@ -328,7 +327,6 @@
 			goto Close;
 	}
 	suspend_console();
-	ftrace_save = __ftrace_enabled_save();
 	suspend_test_start();
 	error = device_suspend(PMSG_SUSPEND);
 	if (error) {
@@ -360,7 +358,6 @@
 	suspend_test_start();
 	device_resume(PMSG_RESUME);
 	suspend_test_finish("resume devices");
-	__ftrace_enabled_restore(ftrace_save);
 	resume_console();
  Close:
 	if (suspend_ops->end)