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/lbux.c

@@ -0,0 +1,25 @@
+#include <stdio.h>
+#include <assert.h>
+
+int main(void)
+{
+    int value, rd;
+    int *p;
+    unsigned long addr, index;
+    int result;
+
+    value  = 0xBCDEF389;
+    p = &value;
+    addr = (unsigned long)p;
+    index  = 0;
+    result = value & 0xFF;
+    __asm
+        ("lbux %0, %1(%2)\n\t"
+         : "=r"(rd)
+         : "r"(index), "r"(addr)
+        );
+
+    assert(rd == result);
+
+    return 0;
+}