Multiple above rows and left columns are checked while generating reference
MV candidate list for the current block. But, for warped ref_mv, we only
generate warped reference MV for current block if one neighbor block is
WARPED_CAUSAL mode and is located in the immediate above row or left column.

Change-Id: Ia9e9c2b7f97b61e0e4d2eeffd8d91e9e5f93d1a0