rockchip: Use common bss and stack addresses on RK356x

Currently the following memory layout is typically used on RK356x:
[    0, 256K) - SPL binary
[ 256K,   2M) - TF-A / reserved
[   -X,   4M) - SPL pre-reloc stack (SPL_STACK)
[-128K,   4M)   - pre-reloc malloc heap (SPL_SYS_MALLOC_F_LEN)
[   -X,   6M) - SPL reloc stack (SPL_STACK_R_ADDR)
[   5M,   6M)   - reloc malloc heap (SPL_STACK_R_MALLOC_SIMPLE_LEN)
[  10M,   +X) - U-Boot proper binary (TEXT_BASE)
[   -X,  12M) - U-Boot proper pre-reloc stack (CUSTOM_SYS_INIT_SP_ADDR)
[-128K,  12M)   - pre-reloc malloc heap (SYS_MALLOC_F_LEN)
[  64M, +16K) - SPL bss (SPL_BSS_START_ADDR, SPL_BSS_MAX_SIZE)

SPL can safely load U-Boot proper + FDT to [10M, 12M-128K) with this
layout.

Migrate to use common bss, stack and malloc heap size and addresses to
remove this size limitation.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
(Update for pinetab2-rk3566_defconfig)
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>