libdasd: Provide definition for bus id size

dasdview and libdasd deal with DASD bus ids and should use a definition
for the size. libu2s already provides a definition, which is used by
dasdview. However, the size of 32 is a bit much and the definition
should be part of libdasd.

Including the terminating null byte ('\0') and considering a DASD bus id
length of 8 characters (e.g. 0.0.4711), this leads to a size of 9.

Provide such a definition via libdasd and update any user.

Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

include/lib/dasd_base.h

@@ -20,6 +20,9 @@
 #include <stdio.h>
 #include <sys/ioctl.h>
 
+/* A bus id of a DASD is 8 characters long. E.g. 0.0.4711 */
+#define DASD_BUS_ID_SIZE	9
+
 typedef struct dasd_information2_t {
 	unsigned int devno;         /* S/390 devno */
 	unsigned int real_devno;    /* for aliases */