disp: msm: sde: update core clk rate during cont-splash

Update the bootloader set core-clk rate to the SDE software
structure when continuous splash is enabled. This will
make sure SDE handles the shift in core-clk rate correctly
when user-mode votes for a different rate with the first
frame.

Change-Id: Ib8e11332578ad154b14793d8ddcfec488be63aef
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>