rtc: ds1685: use devm_platform_ioremap_resource helper

Simplify ioremapping of registers by using devm_platform_ioremap_resource.

Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Acked-by: Joshua Kinard <kumba@gentoo.org>
Link: https://lore.kernel.org/r/20191011150546.9186-2-tbogendoerfer@suse.de


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