mfd: ab8500-sysctrl.c: Provide charging as reset reason

It's possible to supply a string to provide a reason for
triggering a restart. In this case our reason is to enter
charging-only mode, as a charger was found to be present.
Signed-off-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NJonas Aaberg <jonas.aberg@stericsson.com>
Reviewed-by: NKarl KOMIEROWSKI <karl.komierowski@stericsson.com>

drivers/mfd/ab8500-sysctrl.c

@@ -59,7 +59,7 @@ void ab8500_power_off(void)
 			       "Charger \"%s\" is connected with known battery."
 			       " Rebooting.\n",
 			       pss[i]);
-			machine_restart(NULL);
+			machine_restart("charging");
 		}
 	}