twl4030_charger: use devres for power_supply_register and kzalloc.

Final allocations/registrations are now managed by devres.

Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Sebastian Reichel <sre@kernel.org>