[U-Boot] [PATCH v3 13/31] blk: Make blk_next_free_devnum() public

[sjg at google.com]

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

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

Changes in v3: None
Changes in v2: None

 drivers/block/blk-uclass.c |  2 +-
 include/blk.h              | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

Applied to u-boot-dm/next, thanks!