HID: input: Fix NULL pointer dereference when power_supply_register fails

Do not call power_supply_powers() if power_supply_register() failed
earlier. This fixes possible NULL pointer dereference by
power_supply_powers() in such case.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Sebastian Reichel <sre@kernel.org>