vp9_mcomp.c visual studio warnings resolved

Change-Id: I7546cc8db4decbcd094ad76c64385b97666331b0
diff --git a/vp9/encoder/vp9_mcomp.c b/vp9/encoder/vp9_mcomp.c
index 62b33e4..e7df9e2 100644
--- a/vp9/encoder/vp9_mcomp.c
+++ b/vp9/encoder/vp9_mcomp.c
@@ -871,10 +871,10 @@
 
   MV this_mv;
 
-  int bestsad = INT_MAX;
+  unsigned int bestsad = INT_MAX;
   int ref_row, ref_col;
 
-  int thissad;
+  unsigned int thissad;
   const MV fcenter_mv = {center_mv->row >> 3, center_mv->col >> 3};
 
   const int *mvjsadcost = x->nmvjointsadcost;