msm: mdss: set N_MUTIPLIER bit as per different audio sample rate

In the current implementation N_MULTIPLIER bit for audio packets
on HDMI TX controller is not getting set properly. Fix this issue
by setting the multiplier value according to the sample rate set
for audio playback.

Change-Id: I25ab63eeadd5fd08649e9e828dcab83ec1b60161
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>