qaic: fix msg_len check

If we have more than one transaction then, msg_len will not be equal to
last transaction's length. However, it should always be equal to total
length reported by all transactions.

Change-Id: If35767b28f320b521432c410f409301f833b03e5
Signed-off-by: Pratyush Anand <pratanan@codeaurora.org>