msm: vidc: Avoid port reconfigure if pic struct remains same

Sequence change is inferred due to uninitialized pic_struct
variable. And a lot of time spend on handling of sequence change,
which leads to significant delay in thumbnail generation.

Change-Id: I1eba3c0f7e3cbf17ae4610edb726c028c4a14c19
Signed-off-by: Vasantha Balla <vballa@codeaurora.org>