arm64: dts: realtek: rtd16xx: Carve out boot ROM from memory

Update Mjolnir /memory node to exclude 0..0x2dfff from reg entry.
Add this region to /soc ranges instead.

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