dmi-id: Use dynamic sysfs attributes

We can use sysfs attributes with an extra parameter for dmi id
attributes. This makes it possible to use the same callback function
for all attributes, reducing the binary size significantly (-18% on
x86_64.)

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Lennart Poettering <mzxreary@0pointer.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>