Fix:
```
serial/serial.c: In function 'uart_ioctl':
Error: serial/serial.c:1397:46: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
1397 | FAR struct termios *termiosp = (FAR struct termios *)arg;
| ^
Error: serial/serial.c:1419:46: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
1419 | FAR struct termios *termiosp = (FAR struct termios *)arg;
|
```
Signed-off-by: Huang Qi <huangqi3@xiaomi.com>
b250db5dba