remove bogus LWIP_MAKE_U16() define and use PP_NTOHS() in ip4.c instead

src/core/ipv4/ip4.c

@@ -863,7 +863,7 @@ ip4_output_if_opt_src(struct pbuf *p, const ip4_addr_t *src, const ip4_addr_t *d
     IPH_TTL_SET(iphdr, ttl);
     IPH_PROTO_SET(iphdr, proto);
 #if CHECKSUM_GEN_IP_INLINE
-    chk_sum += LWIP_MAKE_U16(proto, ttl);
+    chk_sum += PP_NTOHS(proto | (ttl << 8));
 #endif /* CHECKSUM_GEN_IP_INLINE */
 
     /* dest cannot be NULL here */
@@ -876,7 +876,7 @@ ip4_output_if_opt_src(struct pbuf *p, const ip4_addr_t *src, const ip4_addr_t *d
     IPH_VHL_SET(iphdr, 4, ip_hlen / 4);
     IPH_TOS_SET(iphdr, tos);
 #if CHECKSUM_GEN_IP_INLINE
-    chk_sum += LWIP_MAKE_U16(tos, iphdr->_v_hl);
+    chk_sum += PP_NTOHS(tos | (iphdr->_v_hl << 8));
 #endif /* CHECKSUM_GEN_IP_INLINE */
     IPH_LEN_SET(iphdr, lwip_htons(p->tot_len));
 #if CHECKSUM_GEN_IP_INLINE

src/include/lwip/def.h

@@ -65,13 +65,6 @@ extern "C" {
 #endif
 #endif
 
-/* Endianess-optimized shifting of two u8_t to create one u16_t */
-#if BYTE_ORDER == LITTLE_ENDIAN
-#define LWIP_MAKE_U16(a, b) ((a << 8) | b)
-#else
-#define LWIP_MAKE_U16(a, b) ((b << 8) | a)
-#endif
-
 #if BYTE_ORDER == BIG_ENDIAN
 #define lwip_htons(x) (x)
 #define lwip_ntohs(x) (x)