Cannot able to detect ttyUSB interface with option GSM driver

```
What steps will reproduce the problem?
1. Build Gingerbread kernel (2.6.37) image with options:
CONFIG_USB_SERIAL_WWAN=y
CONFIG_USB_SERIAL_OPTION=y

2. Loaded kernel image on beagleboard, detected option drivers

3. dmesg | grep option
"USB Serial support registered for GSM modem (1-port)
usbcore: registered new interface driver option
option: v0.7.2.1:USB Driver for GSM modems"

4. plugged-in the novatel device on beagleboard

5. but no ttyUSB* found in "ls /dev/ttyUSB* "

I tried the same thing on ubuntu by building for kernel-2.6.37 and ttyUSB* were
successfully detected
```

Original issue reported on code.google.com by `gsi...@nvtl.com` on 17 Nov 2011 at 1:07

Start with the CONFIG_USB_SERIAL_WWAN and CONFIG_USB_SERIAL_OPTION settings, then compare dmesg and ls /dev/ttyUSB* output on the BeagleBoard with the Ubuntu kernel case. Check whether the Novatel device is enumerated and whether the option driver binds to it. Done means the device is detected and the expected ttyUSB interface appears.

Written by the indexing model from the issue text.