In the ac.c, power_supply_register()'s return value is not checked.

As a result, the driver's add() ops may return success
even though the device failed to initialize.

For example, some BIOS may describe two ACADs in the same DSDT.
The second ACAD device will fail to register,
but ACPI driver's add() ops returns sucessfully.
The ACPI device will receive ACPI notification and cause OOPS.

https://bugzilla.redhat.com/show_bug.cgi?id=772730Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Len Brown <len.brown@intel.com>