extcon: Ensure dynamically allocated sysfs attributes are initialised

The operation of lockdep requires that all dynamically allocated sysfs
nodes are initialised using sysfs_attr_init() otherwise lots of warnings
are generated. Ensure that all the dynamically allocated attributes that
extcon generates have this done.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>