lwip: silence uninitialized and fallthrough warnings

components/lwip/component.mk

@@ -30,6 +30,6 @@ endif
 CFLAGS += -Wno-address  # lots of LWIP source files evaluate macros that check address of stack variables
 
 ifeq ($(GCC_NOT_5_2_0), 1)
-else
-netif/ppp/pppos.o: CFLAGS += -Wno-type-limits
-endif
+lwip/src/netif/ppp/ppp.o: CFLAGS += -Wno-uninitialized
+lwip/src/netif/ppp/pppos.o: CFLAGS += -Wno-implicit-fallthrough
+endif