machine:tanaro: Added RTC overlays

In the future, the TANARO will be produced with two possible
RTC variants. Both variants are present in the main devicetree
but are disabled by default. During the installation, one of
the RTCs will be activated via one of the two devicetree overlays.

BCS 746-000877

conf/machine/imx8mguf.conf

@@ -30,6 +30,8 @@ KERNEL_DEVICETREE ?= " \
     keithkoep/guf-tanaro-qp_070wsvgamlli1d.dtb \
     keithkoep/kuk-trizeps8mini-pconxs-edt7cap.dtb \
     keithkoep/kuk-trizeps8mini-pconxs_v3-atm0700.dtb \
+    seconorth/pcf8563-overlay.dtb \
+    seconorth/rx8803-overlay.dtb \
 "
 
 # Due to a mismatch between the vpu driver and our