arm64: dts: apple: s800-0-3: Add PMGR nodes

Add the two PMGR nodes and all known power state subnodes. Since there
are a large number of them, put them in a separate file to include.

Acked-by: Hector Martin <marcan@marcan.st>
Acked-by: Neal Gompa <neal@gompa.dev>
Signed-off-by: Nick Chan <towinchenmi@gmail.com>
Reviewed-by: Neal Gompa <neal@gompa.dev>
Signed-off-by: Sven Peter <sven@svenpeter.dev>