internal/cpu: define kdsaQuery for s390

Patch from Andreas Krebbel.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/201037

From-SVN: r276962

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-f174fdad69cad42309984dfa108d80f2ae8a9f78
+ed1bd343130ab4907750156d3c04a0cef428bf68
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/internal/cpu/cpu_gccgo.c

@@ -184,4 +184,19 @@ struct queryResult klmdQuery() {
     return ret;
 }
 
+struct queryResult kdsaQuery(void)
+  __asm__(GOSYM_PREFIX "internal..z2fcpu.kdsaQuery")
+  __attribute__((no_split_stack));
+
+struct queryResult kdsaQuery() {
+    struct queryResult ret;
+
+    __asm__ ("lghi   %%r0, 0\t\n"  // set function code to 0 (KDSA-Query)
+            "la     %%r1, %[ret]\t\n"
+            ".long  0xb93a0024\t\n"  // kdsa
+            :[ret] "=QRST" (ret) : : "r0", "r1", "cc");
+
+    return ret;
+}
+
 #endif /* defined(__s390x__)  */