target-mips: Add ASE DSP testcases

Add MIPS ASE DSP testcases.

Signed-off-by: Jia Liu <proljc@gmail.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

tests/tcg/mips/mips32-dsp/bitrev.c

@@ -0,0 +1,20 @@
+#include<stdio.h>
+#include<assert.h>
+
+int main()
+{
+    int rd, rt;
+    int result;
+
+    rt     = 0x12345678;
+    result = 0x00001E6A;
+
+    __asm
+        ("bitrev %0, %1\n\t"
+         : "=r"(rd)
+         : "r"(rt)
+        );
+    assert(rd == result);
+
+    return 0;
+}