e.g. dev_err instead of pr_err prints messages in a slightly more
standardized format.

Also, add a few more error messages to track down errors.

Also, some small cleanups of messages.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Dong Aisheng <dong.aisheng@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>