sunxi: Add TPR2 parameter for H616 DRAM driver

It turns out that some H616 and related SoCs (like H313) need TPR2
parameter for proper working. Add it.

Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>