clk: mdss: initialize reference clock during handoff

In the current implementation, reference clock is not being updated
into pll structure during handoff. This causes dsi fifo overflow
issue during fps change in clock update method. This change fixes
issue with initialization of reference clock during handoff.

Change-Id: I631a393e1ed101a22370c55baa51c42cecada953
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>