mfd: twl6040: Handle mclk used for HPPLL and optional internal clock source

On some boards, like omap5-uevm the MCLK is gated by default and in order
to be able to use the High performance modes of twl6040 it need to be
enabled by SW.
Add support for handling the MCLK source clock via CCF.
At the same time lower the print priority of the notification that the 32K
clock is not provided and it is not going to be handled by the driver.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>