mock_i3c_target_tx() did not update *num_sent before returning.

Although some callers may not directly use this value, i3c_send()
passes num_sent to trace_i3c_send(). If the target TX callback does
not initialize *num_sent, the trace output may report an incorrect
or uninitialized value, leading to confusing debugging information.

For example, the following trace was observed:

  mock_i3c_target_tx I3C mock target write 0x12
  i3c_send I3C send 0/1 bytes, ack=1    (expected 1/1 bytes)

This happens because *num_sent was never set by the TX callback.

Fix this by setting:

  *num_sent = to_write;

so that the actual number of transmitted bytes is correctly
propagated back to i3c_send() and reflected in trace output.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
---
 hw/i3c/mock-i3c-target.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/i3c/mock-i3c-target.c b/hw/i3c/mock-i3c-target.c
index 875cd7c7d0..5c913ee49b 100644
--- a/hw/i3c/mock-i3c-target.c
+++ b/hw/i3c/mock-i3c-target.c
@@ -86,6 +86,7 @@ static int mock_i3c_target_tx(I3CTarget *i3c, const uint8_t *data,
         s->buf[s->p_buf] = data[i];
         s->p_buf++;
     }
+    *num_sent = to_write;
     return ret;
 }
 
-- 
2.43.0