PM / Documentation: suspend-and-cpuhotplug.txt: Fix typo

sysfs was expected in this context.
Signed-off-by: NMarcos Paulo de Souza <marcos.souza.org@gmail.com>
Acked-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Documentation/power/suspend-and-cpuhotplug.txt

@@ -29,7 +29,7 @@ More details follow:
 
                                   Write 'mem' to
                                 /sys/power/state
-                                    syfs file
+                                    sysfs file
                                         |
                                         v
                                Acquire pm_mutex lock