power: remove pda_power supply driver

This driver was used for a couple of Intel PXA and Samsung S3C24xx
based PDAs, but all of those are now removed from the kernel, so
the driver itself is no longer useful.

Cc: Anton Vorontsov <cbou@mail.ru>
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>