msm: mdss: dp: fix check for audio support on the sink

The CEA extension block in the EDID data contains a field which
specifies whether the sink supports basic audio. Ensure to read
this field in addition to the audio data blocks to decide if
audio should be routed to the sink or not.

CRs-Fixed: 2014586
Change-Id: I556d4bc0b2c95bdf7fd24fd11eafb96394bf03af
Signed-off-by: Aravind Venkateswaran <aravindh@codeaurora.org>