USB: add new moto_modem driver for some Morotola phones

This should work on a KRZR K1m, and some other Motorola phones that do
not use the "standard" cdc ACM protocol to talk to USB hosts.

Tested-by: Jeff Garzik <jeff@garzik.org>
Cc: Jiang Dejun <a5652c@motorola.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>