GD32V SoC uses divided clock from core-clock for machine timer clock.
Add config of clock divide factor to support GD32V.
Signed-off-by: TOKITA Hiroshi <tokita.hiroshi@gmail.com>
Split Kconfig into individual files for each driver. This improves
overall readability of the Kconfig options.
Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>