power_supply: Add LP8727 charger driver

National Semiconductor LP8727 is the battery charger with Micro/Mini
USB interface. This IC includes below functions:

- I2C interface for accessing user registers
- Single input Li-Ion battery charger
- Charger input ID detection from Micro/Mini USB
- Multiplexing switches on USB, UART

Signed-off-by: Woogyom Kim <milo.kim@ti.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>