Use minor number for device node

Allocate a range of minor numbers and use the minor number as index
when creating the /dev/ethosu<nr> device node.

Change-Id: I76c2a3995ff5087e42a4e95945eb884a4bfb58f6
diff --git a/kernel/ethosu_device.h b/kernel/ethosu_device.h
index 0722814..3afdda8 100644
--- a/kernel/ethosu_device.h
+++ b/kernel/ethosu_device.h
@@ -76,6 +76,7 @@
 int ethosu_dev_init(struct ethosu_device *edev,
 		    struct device *dev,
 		    struct class *class,
+		    dev_t devt,
 		    struct resource *in_queue,
 		    struct resource *out_queue);