encoder: Fix out of bound access of prediction buffer

While calculating the residual for inter 4x4 MB, the intrinsic
instruction reads extra 4-bytes from the prediction buffer

Test: POC in the bug description

Bug: 204704614

Change-Id: I72b5cb8b63351efb60b65ecbb5e7a8c8bc1fcd94
(cherry picked from commit c79d0f5092ccc5add8a34235c354f0aab7de5360)
Merged-In: I72b5cb8b63351efb60b65ecbb5e7a8c8bc1fcd94
3 files changed