boards: shields: add adafruit adalogger featherwing

Add definition for the Adafruit Adalogger Featherwing. This shield
compatible with the Adafruit Feather family is equipped with an SD card
slot and a PCF8524 RTC.

This work is based on the Adafruit Data Logger shield definition.

Signed-off-by: Philip-Dylan Gleonec <philip-dylan@gleonec.bzh>