ENGR00222900 HDMI AUDIO: fix kernel panic when doing suspend-resume test

ENGR00222900 HDMI AUDIO: fix kernel panic when doing suspend-resume test

In MX6 series, HDMI audio driver is responsible for add IEC header to
audio samples. Driver would maintain variables to cover this work.

The old driver would cause memory access exceeding issue:
1. Resume from an playback. In this case, variable maintained by ALSA is
updated while variable maintained by HDMI driver is not updated. The
mmap copy operation would run into error state due to misalignment.
2. underrun!!! The same error would happens as the items above.

In this patch, add variable check while adding IED header.

Signed-off-by: Chen Liangjun <b36089@freescale.com>