power: supply: wm8350-power: Handle error for wm8350_register_irq

As the potential failure of the wm8350_register_irq(),
it should be better to check it and return error if fails.
Also, use 'free_' in order to avoid same code.

Fixes: 14431aa0 ("power_supply: Add support for WM8350 PMU")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>