disp: msm: dsi: check bit clock before bypassing clock set during DMS

This change ensures that if the dsi clock rate is not specified
in the timing modes, setting clkrate_change_pending is not bypassed.

Change-Id: I2475da1e548f29c68a6a4466c5ef540f7f11d553
Signed-off-by: Satya Rama Aditya Pinapala <psraditya30@codeaurora.org>