linux-raspberrypi: Add back UniPi overlays #3462

Job	Run time
Yocto / Approved commit	4s
Yocto / Source mirror IAM role	4s
Yocto / Device info	44s
Yocto / Build	23m 13s
Yocto / Test (cloud, balena-cloud.com, ubuntu-latest)	43m 5s
Yocto / Test (os, balena-cloud.com, ubuntu-latest)	1h 40m 55s
Yocto / Deploy AMI	-1s
Yocto / Deploy to S3	-1s
Yocto / Deploy hostApp	0s
Yocto / All jobs (revpi-connect, balena-cloud.com)	2s
	2h 48m 5s

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