Do not round in get_mv_rate

Author: barrbrain

src/me.rs

@@ -1506,8 +1506,9 @@ fn get_mv_rate(
 ) -> u32 {
   #[inline(always)]
   fn diff_to_rate(diff: i16, allow_high_precision_mv: bool) -> u32 {
-    let d = if allow_high_precision_mv { diff } else { diff / 2 };
-    2 * d.abs().ilog() as u32
+    let d =
+      if allow_high_precision_mv { i32::from(diff) * 2 } else { diff.into() };
+    d.abs().ilog() as u32
   }
 
   diff_to_rate(a.row - b.row, allow_high_precision_mv)