Some of the Alpha PLLs support dynamic update in which the
frequency can be changed dynamically without turning off the PLL.

This dynamic update requires the following sequence:

 1. Write the desired values to L_VAL and ALPHA_VAL registers
 2. Toggle pll_latch_input from low to high
 3. Wait for pll_ack_latch to transition from low to high
    The new L and alpha values have been latched. It may
    take some time for the PLL to fully settle with these
    new values.
 4. Pull pll_latch_input low
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Taniya Das <tdas@codeaurora.org>
Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>