net: Add Kconfig option for BOOTP_NTPSERVER

Add a Kconfig option for BOOTP_NTPSERVER to enable the DHCP/BOOTP option
to configure the sntp server address.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index eb14e08..38406fc 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -1094,6 +1094,10 @@
 	default y
 	depends on CMD_BOOTP
 
+config BOOTP_NTPSERVER
+	bool "Request & store 'ntpserverip' from BOOTP/DHCP server"
+	depends on CMD_BOOTP
+
 config BOOTP_PXE
 	bool "Send PXE client arch to BOOTP/DHCP server"
 	default y