s390/css: indicate the availability of the AIV facility

The patch adds an indication for the presence Adapter Interruption
Virtualization facility (AIV) of the general channel subsystem
characteristics.

Signed-off-by: Michael Mueller <mimu@linux.vnet.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
[change wording]

arch/s390/include/asm/css_chars.h

@@ -20,7 +20,9 @@ struct css_general_char {
 	u32 aif_tdd : 1; /* bit 56 */
 	u32 : 1;
 	u32 qebsm : 1;	 /* bit 58 */
-	u32 : 8;
+	u32 : 2;
+	u32 aiv : 1;     /* bit 61 */
+	u32 : 5;
 	u32 aif_osa : 1; /* bit 67 */
 	u32 : 12;
 	u32 eadm_rf : 1; /* bit 80 */