msm: vidc: Enable LTR use contraint by default

Encoder shall encode subsequent frames in encoding order subject to the 
following constraints:
- It shall not use short-term reference frames in display/input
  order older than the current frame with the LTR command applied
  for future encoding in encoding order.
- It shall not use LTR frames not described by the most recent USELTRFRAME.
- It may use LTR frames updated after the current frame in encoding order.

Change-Id: I167bb0e211c46f892fedb88f8054bc98543ebe8a
Signed-off-by: Akshata Sahukar <asahukar@codeaurora.org>