msm: mdss: hdmi: Proper CEC line busy check

Checks the CEC (Consumer Electronics Control) line for availability
properly so that in case of line being busy it can send re-try
request.

CRs-Fixed: 552367
Change-Id: I75dae23738d791de9a75b78a14e62cd3c40fa2c4
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>