Remove point-on-curve check from |ec_GFp_simple_oct2point|.

In the case of a compressed point, the decompression ensures that the
point is on the curve. In the uncompressed case,
|EC_POINT_set_affine_coordinates_GFp| checks that the point is on the
curve as of 38feb990a1.

Change-Id: Icd69809ae396838b4aef4fa89b3b354560afed55
Reviewed-on: https://boringssl-review.googlesource.com/6487
Reviewed-by: Brian Smith <brian@briansmith.org>
Reviewed-by: Adam Langley <agl@google.com>

crypto/ec/oct.c

@@ -261,12 +261,6 @@ static int ec_GFp_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
     }
   }
 
-  /* test required by X9.62 */
-  if (!EC_POINT_is_on_curve(group, point, ctx)) {
-    OPENSSL_PUT_ERROR(EC, EC_R_POINT_IS_NOT_ON_CURVE);
-    goto err;
-  }
-
   ret = 1;
 
 err: