To ease conversion to driver model, add helper functions which deal with
calling each block device method. With driver model we can reimplement these
functions with the same arguments.

Use inline functions to avoid increasing code size on some boards.

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