msm: vidc: vdec: Set all buffer counts right for thumbnail mode

Set min, actual and host buffer count to 1. This will make sure
that the client gets the buffer count right and allocates the buffer
properly.

Change-Id: I6a4682d675e22725f7382e13f5f3d1b655965224
CRs-Fixed: 2074101
Signed-off-by: Karthikeyan Periasamy <kperiasa@codeaurora.org>