msm: ocmem: Allow pending requests to be cancelled

If a client use case completes before OCMEM is allocated allow the
client to cancel the pending request by making use of the free API.

Change-Id: I3991854963c3fc7e8fafbd88c767ee1166c2a1b4
Signed-off-by: Naveen Ramaraj <nramaraj@codeaurora.org>