msm: vidc: Handle encoder input in true dynamic mode

Earlier video driver maintains list of fds and compare
each ETB fd with these values. If the fd is found then
mapping is retained. But in some usecases, buffer address
and fd association may not be unique. This resuts in
usage of stale buffers. This is also not the true dynamic
buffer mode. With this change, driver treats every buffer
as new buffer and map and unmap each time.

CRs-Fixed: 989007
Change-Id: Ice90c745d4920b64c48c3f4dafca789f2551b327
Signed-off-by: Praneeth Paladugu <ppaladug@codeaurora.org>