[pxe] Populate ciaddr in fake PXE Boot Server ACK packet

We currently do not populate the ciaddr field in the constructed PXE
Boot Server ACK packet.  This causes a WDS server to respond with a
broadcast packet, which is then ignored by wdsmgfw.efi since it does
not match the specified IP address filter.

Fix by populating ciaddr within the constructed PXE Boot Server ACK
packet.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/net/fakedhcp.c

 		return rc;
 	}
 
+	/* Populate ciaddr */
+	fetch_ipv4_setting ( netdev_settings ( netdev ), &ip_setting,
+			     &dhcppkt.dhcphdr->ciaddr );
+
 	/* Merge in ProxyDHCP options */
 	if ( proxy_settings &&
 	     ( ( rc = copy_settings ( &dhcppkt, proxy_settings ) ) != 0 ) ) {