ARM: tegra: nexus7: Add SMB347 battery charger

SMB347 is a battery charger controller which is found on the Nexus 7
device.

Signed-off-by: David Heidelberg <david@ixit.cz>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>