ARMV7: OMAP4: twl6030 add battery charging support

Add battery charging support twl6030 driver.
Add support for battery voltage and current measurements.
Add command to get battery status and start/stop battery charging from USB.

Signed-off-by: Balaji T K <balajitk@ti.com>
Tested-by: Steve Sakoman <steve.sakoman@linaro.org>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>