msm: mdss: fix frame rate calculation for resolution switch

Current resolution switch calculation is using the wrong
values for the fps calculation.
Correct the values, by using the correct pixel clock
value and adjusting if dsc is enabled as well as
use the default fps, for panels where default frame
rate is not 60.

Change-Id: I4be0a9d5d163b0630e8cfeb930e72c32f487ccb1
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>