libmedia: Increase framecount in Track Offload

Track offloading requires higher framecount
to avoid underruns. Fix this, by increasing
the framecount to what the client has requested
for since the client need not start the track
till the requested framecount has been reached

CRs-Fixed: 880862
Change-Id: I1d5e6cb9cb57cdec021a846a4e5b6ea1b68c7271