kernel: Fix rtc-ds1307 dependency on hwmon-core for 4.19

kernel: Fix rtc-ds1307 dependency on hwmon-core for 4.19

It seems, that since Linux 4.18-rc1 rtc-ds1307 depends on hwmon-core.

 commit 6b583a64fd1e019fd01626b46892ebf2361951c5
 Author: Heiner Kallweit <hkallweit1@gmail.com>
 Date:   Wed Sep 27 22:41:26 2017 +0200

    rtc: ds1307: simplify hwmon config

    We don't have to define an extra config symbol, IS_REACHABLE does
    what we need. And having this config symbol just to save the few
    bytes of hwmon support on non-DS3231 chips isn't worth it IMO
    (especially as the symbol is set per default).

While at it, use the same dependency check for `kmod-regmap` as well, so
it's future proof as well.

Signed-off-by: Petr Štetiar <ynezz@true.cz>