twl4030_charger: Make the driver atomic notifier safe

This queues work from the otg notification where the
i2c operations can be safely made. Needed for atomic otg
notifiers.

Signed-off-by: Heikki Krogerus <heikki.krogerus@nokia.com>
Tested-by: Grazvydas Ignotas <notasas@gmail.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>