power: supply: bq27xxx: Fix I2C IRQ race on remove

devm_request_threaded_irq() requested IRQs are only free-ed after
the driver's remove function has ran. So the IRQ could trigger and
call bq27xxx_battery_update() after bq27xxx_battery_teardown() has
already run.

Switch to explicitly free-ing the IRQ in bq27xxx_battery_i2c_remove()
to fix this.

Fixes: 8807feb9 ("power: bq27xxx_battery: Add interrupt handling support")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>