ASoC: msm: Modify buf size check to prevent OOB error

Expected buffer size to read is 2 bytes.
Corrected the size check to return error
when count is not 2.

Change-Id: I43b572d191f6f98a8a790b5ae77b43fabcd7329a
Signed-off-by: Soumya Managoli <smanag@codeaurora.org>