clk: qcom: Update ops for PLLs which support slewing

When enabling the PLL which supports dynamic update of
the frequency, we need to configure it at mid frequency of
the vco frequency range and enable it. Update the PLLs
ops for PLLs which support dynamic update of the frequency.

Change-Id: I7686c6525aa4c3d7473e2dece47191daa6ae6935
Signed-off-by: Veera Vegivada <vvegivad@codeaurora.org>