On a number of machines, qdl could cause crashes on the host
system it ran on, due to swiotlb exaustion.

This seems to be due to 1M buffers being used during the writes.

In order to avoid this, rework qdl_write to break up the writes
into out_maxpktsize chunks.

With this patch, I no longer see host crashes when running qdl

Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Amit Pundir <amit.pundir@linaro.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: dragonboard-aosp@lists.96boards.org
Tested-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
[bjorn: Dropped change of max_payload_size]
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>