[MIPS] Add CONFIG_32BIT to kernel_default_arch_macros for MIPS.
Some of the required structure definitons are defined under this macro.

Change-Id: I7a9a986e371381697dcb56bd8ea362856ffa7509
diff --git a/libc/kernel/arch-mips/asm/msgbuf.h b/libc/kernel/arch-mips/asm/msgbuf.h
index 31a1887..d81da73 100644
--- a/libc/kernel/arch-mips/asm/msgbuf.h
+++ b/libc/kernel/arch-mips/asm/msgbuf.h
@@ -21,18 +21,21 @@
 struct msqid64_ds {
  struct ipc64_perm msg_perm;
 /* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
+ unsigned long __unused1;
  __kernel_time_t msg_stime;
+ unsigned long __unused2;
  __kernel_time_t msg_rtime;
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
+ unsigned long __unused3;
  __kernel_time_t msg_ctime;
  unsigned long msg_cbytes;
-/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  unsigned long msg_qnum;
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  unsigned long msg_qbytes;
  __kernel_pid_t msg_lspid;
  __kernel_pid_t msg_lrpid;
-/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  unsigned long __unused4;
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  unsigned long __unused5;
 };
 #endif
-/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */