clk: ti: clkctrl: support multiple clkctrl nodes under a cm node

Currently, only one clkctrl node can be added under a specific CM node
due to limitation with the implementation. Modify the code to pick-up
clockdomain name from the clkctrl node instead of CM node if provided.
Also, add a new flag to the TI clock driver so that both modes can
be supported simultaneously.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Tested-by: Tony Lindgren <tony@atomide.com>