selftests/user_events: Fix failures caused by test code

In parse_abi function,the dyn_test fails because the
enable_file isn’t closed after successfully registering an event.
By adding wait_for_delete(), the dyn_test now passes as expected.

Link: https://lore.kernel.org/r/20250221033555.326716-1-realxxyq@163.com
Signed-off-by: Yiqian Xun <xunyiqian@kylinos.cn>
Acked-by: Beau Belgrave <beaub@linux.microsoft.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Author: Yiqian Xun

tools/testing/selftests/user_events/dyn_test.c

@@ -127,6 +127,8 @@ static int parse_abi(int *check, const char *value)
 
 	close(fd);
 
+	wait_for_delete();
+
 	return ret;
 }