clk: qcom: clock-pll: Rework test control programming

Variable rate PLLs may require an initial value to be
programmed into the test control registers, or require
test control programming as part of the enable sequence.
Provide for both options.

Change-Id: Ie1d1b3859aa87d31416220dae62118c9c88d0693
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>