Add new driver to use tethering with an iPhone device. After initial submission,
apply fixes to fit the new driver into the kernel standards.

There are still a couple of minor (almost cosmetic-level) issues, but the driver
is fully functional right now.
Signed-off-by: L. Alberto Giménez <agimenez@sysvalve.es>
Signed-off-by: Diego Giagio <diego@giagio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>