max8903_charger: Convert to using managed resources

Use managed resource functions devm_request_threaded_irq and
devm_power_supply_register to simplify error handling.

To be compatible with the change, various gotos are replaced
with direct returns and unneeded labels are dropped. Also,
remove max8903_remove as it is now redundant.

Signed-off-by: Vaishali Thakkar <vthakkar1994@gmail.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>