msm: mdss: hdmi: Add sysfs nodes for audio/video data

Add sysfs nodes to provide SAD (Short Audio Descriptor) data
like supported sampling frequency, bit rate, formats and
speaker allocation data block inforamtion so that different
modules can access this data for their internal processing.

Change-Id: I4fcbe6e517d888052f0b4cfd29e0e6ee6fc88395
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>