MFC r349072, r349316-r349318

MFC r349072, r349316-r349318

r349072:
Remove pcf8563reg.h, the driver it was associated with was replaced in 2017
with the nxprtc multi-chip driver.

r349316:
Remove some unused header files from the ad7418 driver.

r349317:
Add the rtc8583 driver to conf/files.  Also, move sy8106a from
file.allwinner to conf/files... it's not allwinner-specific, some day
other platforms could use the same regulator chip.

r349318:
The sy8106a and syr827 drviers require FDT and the ext_resources subsystem.