libertas: sysfs interface for accessing non-volatile configuration

This will create the following sysfs directories:
/sys/class/net/mshX
		...
		|-- boot_options
		|   |-- bootflag
		|   `-- boottime
		...
		|-- mesh_ie
		|   |-- capability
		|   |-- mesh_id
		|   |-- metric_id
		|   `-- protocol_id

Signed-off-by: Javier Cardona <javier@cozybit.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>