arm64: dts: renesas: falcon: Move console config to CPU board DTS

The serial console is located on the Falcon CPU board.  Hence move
serial console configuration from the main Falcon DTS file to the DTS
file that describes the CPU board.

Fixes: 63070d7c ("arm64: dts: renesas: Add Renesas Falcon boards support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/20210316154705.2433528-2-geert+renesas@glider.be