rockchip: Move imply ROCKCHIP_COMMON_STACK_ADDR under SoC Kconfig symbol

rockchip: Move imply ROCKCHIP_COMMON_STACK_ADDR under SoC Kconfig symbol

The ROCKCHIP_COMMON_STACK_ADDR Kconfig option was originally enabled
in the SoC specific Kconfig files to ease during the initial migration
to use common stack addresses.

All boards for the affected SoCs have been migrated to use common stack
addresses. Migrate to use an imply under the SoC symbol instead of
re-define the symbol in each SoC specific Kconfig file.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>