[PATCH] Sysfs not handling show errors

[PATCH] Sysfs not handling show errors

Originally by Rusty Lynch, munged by me, acked
by Mochel.

 Attempting to cat a sysfs file that returns an error will result in an
 endless dump of garbage to the screen because the result of the specific
 show operation was being saved to a size_t (unsigned) and then later
 checked for a negative value.