USB: fix needless failure under certain conditions

in devices.c we have a piece of code for dealing with losing in a race.
If we indeed lose the race we don't care whether our own memory allocation
worked. The check for that is so early that we return early even if we
don't have to.

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