msm_fb: hdmi: Proper update of ACR CTRL Register

While changing the audio sampling rate, the older data in
the control register needs to cleaned before writing in
new data to avoid mixed or wrong data writing.

CRs-Fixed: 405772
Change-Id: I95d0807ea8cf544e4a0c8caed00de6cd60352efa
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>