raspberry-pi{,0,3,4}: enable swclock (MR 1336)

Following discussions in
https://gitlab.com/postmarketOS/pmaports/-/issues/398, swclock has been
removed from postmarketos-base to avoid setting time incorrectly on
devices with a hardware clock. The various raspberry pi don't have
an hardware clock. This activate swclock back.

device/testing/device-raspberry-pi4/device-raspberry-pi4.post-install

@@ -1,4 +1,6 @@
 #!/bin/sh
 
+rc-service add swclock boot
+
 cd /boot/dtbs-rpi4/
 find . -type f -regex ".*\.dtbo\?$" -exec install -Dm644 {} /boot/{} \;