rts: ds1685: remove not needed fields from private struct

A few of the fields in struct ds1685_priv aren't needed at all,
so we can remove it.

Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Acked-by: Joshua Kinard <kumba@gentoo.org>
Link: https://lore.kernel.org/r/20191011150546.9186-1-tbogendoerfer@suse.de


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>