clk: qcom: clk-alpha-pll: Update implementation for Zonda PLL

The Zonda PLL has a 16 bit signed alpha and in the cases where the alpha
value is greater than 0.5, the L value needs to be adjusted accordingly.

Thus update the logic for the same.

Change-Id: Id3163dc53e66cc8dcd5e61d6e997ef24b6cf3534
Signed-off-by: Taniya Das <tdas@codeaurora.org>