remove two lines to prevent crash during compile for the mbed frdm k64f

Dependencies:   Socket lwip-eth lwip-sys lwip

Fork of EthernetInterface by mbed official

Revision:
55:84000bbe55af
Parent:
54:183490eb1b4a
Child:
56:16def471e387
diff -r 183490eb1b4a -r 84000bbe55af lwip-eth.lib
--- a/lwip-eth.lib	Wed May 11 22:18:04 2016 +0000
+++ b/lwip-eth.lib	Fri Apr 14 13:42:13 2017 +0000
@@ -1,1 +1,1 @@
-http://mbed.org/users/mbed_official/code/lwip-eth/#da93f0f73711
+http://mbed.org/users/mbed_official/code/lwip-eth/#6987f08bc079