drbd: The minor_count module parameter is only a hint nowadays

* The max of minor_count is 255
* In drbdadm count the number of minors, instead of finding
  the highest minor number
* No longer us the magic in the init script
Signed-off-by: NPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: NLars Ellenberg <lars.ellenberg@linbit.com>

include/linux/drbd_limits.h

@@ -16,7 +16,7 @@
 #define DEBUG_RANGE_CHECK 0
 
 #define DRBD_MINOR_COUNT_MIN 1
-#define DRBD_MINOR_COUNT_MAX (1U << 20)
+#define DRBD_MINOR_COUNT_MAX 255
 #define DRBD_MINOR_COUNT_DEF 32
 #define DRBD_MINOR_COUNT_SCALE '1'