mm-core: Increase max instance value to 16

Venus firmware currently supports eight decoder and
encoder instances simultaneously and this value may
be increased in near future. But OMX core was giving
support only for four concurrent instances. This
change enhanced OMX core capability to support sixteen
concurrent instances.

Change-Id: I1c3c1861d2ea3df62d72201304259f75589523a7
CRs-fixed: 576884
9 files changed