msm: vidc: Set ltr mode to manual when enabled by client

LTR Manual Mode is the only mode supported and hence should be
selected whenever LTR is set. Because mode was uninitialized
the property was rejected in hfi packetization.

CRs-Fixed: 2214781
Change-Id: I57aa879b433a43168c8b1c51fb05c0822e7b9bde
Signed-off-by: Chinmay Sawarkar <chinmays@codeaurora.org>