Vectorize erfc(x) for double and improve erfc(x) for float.

Eigen/src/Core/arch/SVE/PacketMath.h

@@ -360,7 +360,8 @@ struct packet_traits<float> : default_packet_traits {
     HasExp = 1,
     HasSqrt = 1,
     HasTanh = EIGEN_FAST_MATH,
-    HasErf = EIGEN_FAST_MATH
+    HasErf = EIGEN_FAST_MATH,
+    HasErfc = EIGEN_FAST_MATH
   };
 };