added default placement macro for all boards and toolchains

Author: sg-

net/LWIPInterface/lwip/core/mem.c

@@ -189,11 +189,13 @@ struct mem {
 #elif defined(TARGET_LPC1768)
 #  if defined (__ICCARM__)
 #     define ETHMEM_SECTION
-#  elif defined(TOOLCHAIN_GCC_CR)
+#  elif defined(TOOLCHAIN_GCC_CR) || defined(TOOLCHAIN_GCC_ARM)
 #     define ETHMEM_SECTION __attribute__((section(".data.$RamPeriph32")))
 #  else
 #     define ETHMEM_SECTION __attribute__((section("AHBSRAM0"),aligned))
 #  endif
+#else
+#define ETHMEM_SECTION
 #endif
 
 /** the heap. we need one struct mem at the end and some room for alignment */

net/LWIPInterface/lwip/core/memp.c

@@ -174,6 +174,8 @@ static u8_t *const memp_bases[] = {
 #  else
 #     define ETHMEM_SECTION __attribute__((section("AHBSRAM1"),aligned))
 #  endif
+#else
+#define ETHMEM_SECTION
 #endif
 
 /** This is the actual memory used by the pools (all pools in one big block). */