RISC-V: configs: enable I2C_DESIGNWARE_CORE with I2C_DESIGNWARE_PLATFORM

The dependency handling of the Synopsys DesignWare I2C
adapter drivers is going to be changed so that the glue
drivers for the PCI and platform buses depend on
I2C_DESIGNWARE_CORE.

Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: linux-riscv@lists.infradead.org
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>