include: riscv: linker: add missing generate linker sections from dt
include: riscv: linker: add missing generate linker sections from dt

Riscv platfrom includes linker dt regions (LINKER_DT_REGIONS)
but was missing functionality to generate linker sections
from zephyr,memory-region dt nodes.

Signed-off-by: Lukasz Stepnicki <b29c57f875e23ee93930386fa9cdebce26f164a7@nordicsemi.no>

galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr