arm64: dts: realtek: rtd16xx: Add memory reservations

Reserve memory regions for RPC and TEE.

Fixes: d8a6c3b3 ("arm64: dts: realtek: Add RTD1619 SoC and Realtek Mjolnir EVB")
Acked-by: James Tai <james.tai@realtek.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>