USB: Sierra Wireless driver update

The largest feature in this patch is that it adds significant throughput
increase to the Sierra driver and adds support for modem status line
control (e.g. the DTR line). This patch also updates the current sierra.c
driver so that it supports both 3-port Sierra devices and 1-port legacy
devices and removes Sierra's references in other related files (Kconfig and
airprime.c).

Signed-off-by: Kevin Lloyd <linux@sierrawireless.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>