log(9) variant for device error messages

[Martin Husemann <martin%duskware.de@localhost>]

The aprint_error_dev() function is probably one of the most abused aprint_*
family functions in drivers, because it is SO usefull.

However, the abuse of aprint_* for messages past autoconfiguration has to
stop. It would be good to have a good replacement in the log(9) family.

So I propose to create

        void log_device_error(device_t, const char *format, ...);

which prepends the message with device_xname() and ": ", and passes it
as LOG_ERR to log(9).

What do you think?

Martin