ASoC: hdac_hdmi: tidy up a memset()

The ARRAY_SIZE() is the number of the elements but we want to use the
number of bytes.  Fortunately, in this case the value is the same so it
doesn't affect runtime.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200825104623.GA278587@mwanda


Signed-off-by: Mark Brown <broonie@kernel.org>