rockchip: enable SPL_SYSRESET config for all Rockchip SoCs

With Makefiles testing for $(SPL_TPL_)SYSRESET, we need SPL_SYSRESET
for do_reset() in SPL for Rockchip SoCs.

References: 87c16d49 "drivers: spl: consistently use the $(SPL_TPL_) macro"
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>