sd-device: chase sysattr and refuse to read/write files outside of sysfs

sd-device: chase sysattr and refuse to read/write files outside of sysfs

This makes sd_device_get_sysattr_value()/sd_device_set_sysattr_value()
refuse to read/write files outside of sysfs for safety.

Also this makes
- use chase() to resolve and open the symlink in path to sysfs attribute,
- use delete_trailing_chars(),
- include error code in cache entry, so we can cache more error cases,
- refuse caching value written to uevent file of any devices, i.e.
  sd_device_set_sysattr_value(dev, "../uevent", "add") will also not
  cache the value "add".