net: qrtr: Move resume-tx transmission to recvmsg

The confirm-rx bit is used to implement a per port flow control, in
order to make sure that no messages are dropped due to resource
exhaustion. Move the resume-tx transmission to recvmsg to only confirm
messages as they are consumed by the application.

Change-Id: I616045b66f5fe227308d559007852afbceca2d07
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Git-commit: ddef359a31b63e8755f95c5cc82d659c4386f7fd
Git-repo: https://github.com/andersson/kernel.git


[clew@codeaurora.org: checkpatch format warnings and remove extra
 variables]
Signed-off-by: Chris Lew <clew@codeaurora.org>