Define sysfs max buffer size

Define sysfs max buffer size

sysfs_get_str() usages have inconsistant buffer size.
This results in wild buffer declarations and redundant memory usage.

Define maximum buffer size for sysfs strings.
Replace wild sysfs string buffer sizes for globaly defined value.

Signed-off-by: Mateusz Kusiak <mateusz.kusiak@intel.com>
Signed-off-by: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>