driver: add sysfs_driver:get_attr()
attribute: add lua binding specific methods for accessing 'struct sysfs_attribute' members
device: add sysfs_device:get_attr()
attribute: change sysfs_attribute object to use 'generic' userdata type with no weak reference
device: remove bogus 'else' in lua_sysfs_device_iterator()
device: move lua_sysfs_device_iterator() out of the object definition
attribute: add internal sysfs attribute iterator function

Note:

This function is used by object specific iterator functions to iterate over
a sysfs dlist containing attributes.
device: add sysfs_device:get_attributes() iterator