power: remove tosa_battery driver

The PXA tosa machine is removed, so this driver is no longer
in use.

Cc: linux-pm@vger.kernel.org
Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>