power: supply: ab8500_charger: Bail out in case of error in 'ab8500_charger_init_hw_registers()'

If an error occurs when we enable the backup battery charging, we should
go through the error handling path directly.

Before commit db43e6c4 ("ab8500-bm: Add usb power path support") this
was the case, but this commit has added some code between the last test and
the 'out' label.
So, in case of error, this added code is executed and the error may be
silently ignored.

Fix it by adding the missing 'goto out', as done in all other error
handling paths.

Fixes: db43e6c4 ("ab8500-bm: Add usb power path support")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>