clk: ti: clkctrl: replace dashes from clkdm name with underscore

The change in the DTS data node naming prevents using underscore
within the node names and force usage of dash instead. On the other
hand, clockdomains use underscore instead of dash, so this must be
replaced within the driver code so that the mapping between the two
can be done properly.

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