net: ipa: record proper RX transaction count

Each time we are notified that some number of transactions on an RX
channel has completed, we record the number of bytes that have been
transferred since the previous notification.  We also track the
number of transactions completed, but that is not currently being
calculated correctly; we're currently counting the number of such
notifications, but each notification can represent many transaction
completions.  Fix this.

Fixes: 650d1603

 ("soc: qcom: ipa: the generic software interface")
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>