linux-wandboard

USB: add helper to convert USB error codes

This converts error codes specific to USB to generic error codes
that can be returned to user space. Tests showed that it is so small
that it is better inlined.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>