msm: ipc: Append alignment bytes to loopback packet

When messages are looped back to the local port, the sender does not
append the alignment bytes while the receiver is discarding the
alignment bytes. This leads to receiver receiving an incomplete message.

Fix this issue by appending the alignment bytes in the loopback path.

Change-Id: Ie340e5311e15e39558a8fe9c95a54da686df4371
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>