trats/trats2: exynos_power_init: return 0 if no battery detected.

trats/trats2: exynos_power_init: return 0 if no battery detected.

Generic board support is now enabled for Exynos 4, and if any
init function returns an error then the init process is stopped.

This makes a boot issue on the Trats and Trats2 devices. If the device
is supplied by USB cable or an external power supply then it can't boot
because function exynos_power_init returns an error. Now this function
returns 0 if battery is not connected.

Signed-off-by: Przemyslaw Marczak <[email protected]>
Cc: Lukasz Majewski <[email protected]>
Cc: Piotr Wilczek <[email protected]>
Cc: Minkyu Kang <[email protected]>
Signed-off-by: Minkyu Kang <[email protected]>