riscv: cpu: jh7110: Imply SPL_SYS_MALLOC_CLEAR_ON_INIT

riscv: cpu: jh7110: Imply SPL_SYS_MALLOC_CLEAR_ON_INIT

Starfive JH7110 needs to clear L2 LIM to zero before use or ECC error
would be triggered. Currently, we use DDR ram for SPL malloc arena on
Visionfive 2 board in defconfig, but it's also possible to use L2 LIM as
SPL malloc arena. To avoid triggering ECC error in this scenario, we
imply SPL_SYS_MALLOC_CLEAR_ON_INIT as default.

Signed-off-by: Bo Gan <ganboing@gmail.com>
Signed-off-by: Shengyu Qu <wiagn233@outlook.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>