dm: blk: Do not use uclass_next_device_err

dm: blk: Do not use uclass_next_device_err

blk_first_device_err/blk_next_device_err uses
uclass_first_device_err/uclass_next_device_err for device iteration.

Although the function names superficially match the return value from
uclass_first_device_err/uclass_next_device_err is never used
meaningfully, and uclass_first_device/uclass_next_device works equally
well for this purpose.

In the following patch the semantic of
uclass_first_device_err/uclass_next_device_err will be changed to be
based on uclass_first_device_check/uclass_next_device_check breaking
this sole user that uses uclass_next_device_err for iteration.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Reviewed-by: Simon Glass <sjg@chromium.org>