riscv: Add da9063_pmic and da9063_rtc to GENERIC and NOTES

This is the PMIC on SiFive's HiFive Unmatched; add it and the RTC child
device driver so we have a working RTC.

Reviewed by: mhorne, imp
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D36201

(cherry picked from commit 100f79569dbcee9a7c66f8fe543fa04e8bfb04bd)