Fix cfg fuzz

I did not investigate too much into trying to figure out how the
encoding for simple crypto works. I made some simple changes(basically
disabled the checks for uncompressed keys) and atleast it works for
uncompressed keys roundtrip.

secp256k1-sys/src/lib.rs

@@ -816,8 +816,7 @@ mod fuzz_dummy {
                     0
                 } else {
                     ptr::copy(input.offset(1), (*pk).0.as_mut_ptr(), 64);
-                    test_cleanup_pk(pk);
-                    test_pk_validate(cx, pk)
+                    1
                 }
             },
             _ => 0
@@ -830,9 +829,9 @@ mod fuzz_dummy {
                                                 compressed: c_uint)
                                                 -> c_int {
         check_context_flags(cx, 0);
-        assert_eq!(test_pk_validate(cx, pk), 1);
         if compressed == SECP256K1_SER_COMPRESSED {
             assert_eq!(*out_len, 33);
+            assert_eq!(test_pk_validate(cx, pk), 1);
             if (*pk).0[32] <= 0x7f {
                 *output = 2;
             } else {