Current driver only supports registering fixed rate clocks from DT. Add
new API which makes it possible to register fixed rate clocks directly
from e.g. platform specific clock drivers.
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tero Kristo <kristo@kernel.org>