soc: qcom: mdt_loader: be more informative on errors

In __qcom_mdt_load() there are cases where an error occurs that
cause a message to be printed.  In some of those cases the errno
value can be helpful to understand exactly what caused the problem.

Print the errno (as well as the firmware file name) where it is
helpful, and in a few cases reword the error message.  Consistently
use the private fw_name for the file name.

Signed-off-by: Alex Elder <elder@linaro.org>
Link: https://lore.kernel.org/r/20210315144455.1770492-1-elder@linaro.org


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>