USB: serial: add qualcomm wireless modem driver

Driver originally written by Qualcomm, but rewritten by me due to the
totally different coding style.  Cleaned up the probe logic to make a
bit more sense, this is one wierd device.  They could have prevented all
of this by just writing sane firmware for the modem.

Cc: Tamm Liu <tamml@qualcomm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>