clk: msm: clock-cpu-8996: Provide an option to use the alternate pll

Provide a commandline switch that will allow the CPUs to use
the alternate PLL as the primary PLL. The dedicated primary
PLLs are unused in this configuration.

Change-Id: Idedffdcf790ebf5ab7a515687ae7a08abe85c540
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>