return -EFAULT on copy_to_user errors

copy_to_user() returns the number of bytes remaining to be copied, but
we want to return a negative error code here.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Ismael Luceno <ismael.luceno@corp.bluecherry.net>
Split assignments from the "if" statements
Fix indentation