The bank0 ram size should be the DRAM size minus reserved size,
the DRAM size may be 1GB, 2GB, 4GB, we can not hard code it.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Added DECLARE_GLOBAL_DATA_PTR for RK3328, RK3368 and RK3399:
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>