Add isa_defs for MIPS

GCC for MIPS only defines _LP64 when 64bit,
while no _ILP32 defined when 32bit.

Signed-off-by: YunQiang Su <syq@debian.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #4712

lib/libspl/include/sys/isa_defs.h

@@ -172,7 +172,28 @@ extern "C" {
 #define	_BIG_ENDIAN
 #define	_SUNOS_VTOC_16
 
-#else /* Currently x86_64, i386, arm, powerpc, s390, and sparc are supported */
+/* MIPS arch specific defines */
+#elif defined(__mips__)
+
+#if defined(__MIPSEB__)
+#define	_BIG_ENDIAN
+#elif defined(__MIPSEL__)
+#define	_LITTLE_ENDIAN
+#else
+#error MIPS no endian specified
+#endif
+
+#ifndef _LP64
+#define	_ILP32
+#endif
+
+#define	_SUNOS_VTOC_16
+
+#else
+/*
+ * Currently supported:
+ * x86_64, i386, arm, powerpc, s390, sparc, and mips
+ */
 #error "Unsupported ISA type"
 #endif