Fix recompile reason logging (pytorch#148200)

for the following test case

```
        @torch.compile(dynamic=False, backend=cnts)
        def fn(x, y, z):
            return x * y * z[0]

        fn(1, torch.randn(1), {0: torch.randn(1)})
        fn(2, torch.randn(2), {0: torch.randn(2)})
        fn(3, torch.randn(3), {0: torch.randn(3)})
        fn(4, torch.randn(4), {0: torch.randn(4)})
        fn(5, torch.randn(5), {0: torch.randn(5)})
```

previously we would log

```
0/0: L['x'] == 1
0/0: L['x'] == 1
0/0: L['x'] == 1
0/0: L['x'] == 1
```

but after this change we now log

```
0/0: L['x'] == 1
0/1: L['x'] == 2
0/2: L['x'] == 3
0/3: L['x'] == 4
```

Pull Request resolved: pytorch#148200
Approved by: https://github.com/xmfan

Author: bobrenjc93

torch/_dynamo/convert_frame.py

@@ -945,7 +945,7 @@ def count_args(code: CodeType) -> int:
         if is_recompilation(cache_size) and frame:
             reasons = get_and_maybe_log_recompilation_reasons(cache_entry, frame)
             recompile_reason = (
-                "Unable to find recompilation reasons" if not reasons else reasons[-1]
+                "Unable to find recompilation reasons" if not reasons else reasons[0]
             )
         metrics_context.update_outer({"recompile_reason": recompile_reason})