memshare: Donot re-allocate the memory for the clients

Currently memshare driver re-allocates the memory for client
if the request comes over old modem design. This patch uses the
existing memory allocated for the client and on request
sends the same.

Change-Id: I1542938c4d0b71a80015b92a417505468e9bb5fc
CRs-Fixed: 689538
Signed-off-by: Katish Paran <kparan@codeaurora.org>