arm: da850-evm: Enable DM and device tree support for da850-evm

With the device tree ported and DM compatible drivers, enable:
OF_CONTROL, DM_SPI, DM_SPI_FLASH and DM_SERIAL

Note: DM_SERIAL is not enabled for da850evm_direct_nor_defconfig
yet.

Reviewed-by: Jagan Teki <jagan@openedev.com>
Signed-off-by: Adam Ford <aford173@gmail.com>