disp: pll: remove recalculation of vco rate

In continuous splash use cases, the display is enabled in
the boot-loader. During display kernel probe, to enable clocks,
the rate is calculated by reading the hardware registers before 
the corresponding software rate is set. At times when these rates
are nearly equal, the call for set rate never happens. This can
cause abnormal behavior. In this change during hand-off we don't
recalculate the clock rate to ensure the software programs the clock
registers accordingly.

Change-Id: I421c523ffd48a0cb73d7721c6d74c8e68aa6d9a5
Signed-off-by: Satya Rama Aditya Pinapala <psraditya30@codeaurora.org>