power: supply: Add dependency to lego-ev3-battery Kconfig options

This battery appears only to be used by a single board (DA850), so it
makes sense to add this to the Kconfig file so that users don't build
the module unnecessarily. It currently seems to be built for the x86
Arch Linux kernel where it's probably not doing much good.

Signed-off-by: Alex Dewar <alex.dewar90@gmail.com>
Acked-by: David Lechner <david@lechnology.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>