s390x/cpumodel: document S390FeatDef.bit not applicable

The 'bit' field of the 'S390FeatDef' structure is not applicable to all
its instances. Currently this field is not applicable, and remains
unused, iff the feature is of type S390_FEAT_TYPE_MISC. Having the value 0
specified for multiple such feature definitions was a little confusing,
as it's a perfectly legit bit value, and as the value of the bit
field is usually ought to be unique for each feature of a given
feature type.

Let us introduce a specialized macro for defining features of type
S390_FEAT_TYPE_MISC so, that one does not have to specify neither bit nor
type (as the latter is implied).
Signed-off-by: NHalil Pasic <pasic@linux.vnet.ibm.com>
Message-Id: <20180221165628.78946-1-pasic@linux.vnet.ibm.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Acked-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>

target/s390x/cpu_features.c

@@ -23,6 +23,10 @@
         .desc = _desc,                               \
     }
 
+/* S390FeatDef.bit is not applicable as there is no feature block. */
+#define FEAT_INIT_MISC(_name, _desc)                 \
+            FEAT_INIT(_name, S390_FEAT_TYPE_MISC, 0, _desc)
+
 /* indexed by feature number for easy lookup */
 static const S390FeatDef s390_features[] = {
     FEAT_INIT("esan3", S390_FEAT_TYPE_STFL, 0, "Instructions marked as n3"),
@@ -123,8 +127,8 @@ static const S390FeatDef s390_features[] = {
     FEAT_INIT("ib", S390_FEAT_TYPE_SCLP_CPU, 42, "SIE: Intervention bypass facility"),
     FEAT_INIT("cei", S390_FEAT_TYPE_SCLP_CPU, 43, "SIE: Conditional-external-interception facility"),
 
-    FEAT_INIT("dateh2", S390_FEAT_TYPE_MISC, 0, "DAT-enhancement facility 2"),
-    FEAT_INIT("cmm", S390_FEAT_TYPE_MISC, 0, "Collaborative-memory-management facility"),
+    FEAT_INIT_MISC("dateh2", "DAT-enhancement facility 2"),
+    FEAT_INIT_MISC("cmm", "Collaborative-memory-management facility"),
 
     FEAT_INIT("plo-cl", S390_FEAT_TYPE_PLO, 0, "PLO Compare and load (32 bit in general registers)"),
     FEAT_INIT("plo-clg", S390_FEAT_TYPE_PLO, 1, "PLO Compare and load (64 bit in parameter list)"),