mfd: ab8500-sysctrl: Update correct turn on status

In L9540, turn_on_status register is not updated correctly if
the device is rebooted with AC/USB charger connected. Due to
this, the device boots android instead of entering into charge
only mode. Read the AC/USB status register to detect the charger
presence and update the turn on status manually.

Signed-off-by: Rajkumar Kasirajan <rajkumar.kasirajan@stericsson.com>
Signed-off-by: Per Forlin <per.forlin@stericsson.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Rupesh KUMAR <rupesh.kumar@stericsson.com>
Reviewed-by: Philippe LANGLAIS <philippe.langlais@stericsson.com>
Tested-by: Rupesh KUMAR <rupesh.kumar@stericsson.com>
Tested-by: Philippe LANGLAIS <philippe.langlais@stericsson.com>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>