rockchip: rk3328: fix syscon id table

syscon id table need a dummy member as NULL ending, or else system
will panic while try to match a compatible in this table as a list.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>