clk: twl6040: Register the clock as of_clk_provider

In order ot be able to use the pdmclk clock via DT it need to be registered
as of_clk_provide.
Since the twl6040 clock driver does not have it's own DT node, use the
parent's node for registering.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>