ecc.rs: Clarify PartialEq impl for ecc::Point

When comparing two points at the gadget-level, we are only
interested in whether their values are equal: we don't care if
the two points come from different chips.

src/circuit/gadget/ecc.rs

@@ -220,12 +220,22 @@ where
 }
 
 /// An elliptic curve point over the given curve.
-#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+#[derive(Copy, Clone, Debug)]
 pub struct Point<C: CurveAffine, EccChip: EccInstructions<C> + Clone + Debug + Eq> {
     chip: EccChip,
     inner: EccChip::Point,
 }
 
+impl<C: CurveAffine, EccChip: EccInstructions<C> + Clone + Debug + Eq> PartialEq
+    for Point<C, EccChip>
+{
+    fn eq(&self, other: &Self) -> bool {
+        self.inner == other.inner
+    }
+}
+
+impl<C: CurveAffine, EccChip: EccInstructions<C> + Clone + Debug + Eq> Eq for Point<C, EccChip> {}
+
 impl<C: CurveAffine, EccChip: EccInstructions<C> + Clone + Debug + Eq> Point<C, EccChip> {
     /// Constructs a new point with the given value.
     pub fn new(