rockchip: ringneck_px30: Use common bss and stack addresses

U-Boot proper pre-reloc is currently running out of memory and it is
thus impossible to boot into U-Boot CLI.

Fix this by migrating to the common bss and stack addresses for PX30,
which drastically increases the size of the pre-reloc allocation pool (8
times bigger now). The memory layout in SPL and U-Boot proper now
match the other SoCs' using ROCKCHIP_COMMON_STACK_ADDR.

Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>