Properly set interp filter used by simple_motion_search

Currently, simple_motion_search does not explicitly set the
interpolation filter, which can hold leftover values from previous
encoding, resulting in inconsistent output.

This commit explicitly sets it to EIGHTTAP_REGULAR.

STATS_CHANGED

Change-Id: Ifae851237c96809b3010ed371098a757acbe7eab
diff --git a/av1/encoder/mcomp.c b/av1/encoder/mcomp.c
index 0eabacb..c05ff71 100644
--- a/av1/encoder/mcomp.c
+++ b/av1/encoder/mcomp.c
@@ -3078,6 +3078,7 @@
   mbmi->ref_frame[0] = ref;
   mbmi->ref_frame[1] = NONE_FRAME;
   mbmi->motion_mode = SIMPLE_TRANSLATION;
+  mbmi->interp_filters = av1_broadcast_interp_filter(EIGHTTAP_REGULAR);
 
   const YV12_BUFFER_CONFIG *yv12 = get_ref_frame_yv12_buf(cm, ref);
   const YV12_BUFFER_CONFIG *scaled_ref_frame =