NETUTILS_DHCPC_RECV_TIMEOUT -> NETUTILS_DHCPC_RECV_TIMEOUT_MS
Recently its unit has been changed from second to millisecond. [1]
Using the same Kconfig name for a different meaning is a pitfall
for an upgrade. I was using 3ms timeout because of this.
This commit renames it so that at least the default value
is used for a careless user like me.
[1]
```
commit 8fd4b6105be2a535ecea2312858602d9ffa4e670
Author: zrrong <zrrong@bouffalolab.com>
Date: Fri May 27 11:35:23 2022 +0800
netutils/dhcpc: Change the timeout unit to milliseconds
```
83505e217b