soc: qcom: mem-buf: Fix message processing race condition

mem-buf currently uses a workqueue with multiple worker threads
associated with it for handling allocation requests and reclaiming
memory. This can cause overlaps in time where an allocation request
can overlap with memory reclaim.

This is not ideal, as the memory allocation request may fail if the
memory that is supposed to have been reclaimed has not been reclaimed
yet. Thus, use an ordered workqueue to make sure that there is no
overlap between processing allocation and memory reclaim messages.

Change-Id: I4a76c74b1785d2448c6c2f97a43efaa5bf6ad99a
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>