blk: Make blk_next_free_devnum() public

blk_next_free_devnum() can be helpful in some cases. Make it
a public API.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/block/blk-uclass.c

@@ -517,7 +517,7 @@ int blk_find_max_devnum(enum if_type if_type)
 	return max_devnum;
 }
 
-static int blk_next_free_devnum(enum if_type if_type)
+int blk_next_free_devnum(enum if_type if_type)
 {
 	int ret;
 

include/blk.h

@@ -378,6 +378,17 @@ int blk_unbind_all(int if_type);
  */
 int blk_find_max_devnum(enum if_type if_type);
 
+/**
+ * blk_next_free_devnum() - get the next device number for an interface type
+ *
+ * Finds the next number that is safe to use for a newly allocated device for
+ * an interface type @if_type.
+ *
+ * @if_type:	Interface type to scan
+ * @return next device number safe to use, or -ve on error
+ */
+int blk_next_free_devnum(enum if_type if_type);
+
 /**
  * blk_select_hwpart() - select a hardware partition
  *