Error seen while using reference RIL for an external GSM modem on AM18x running Android-2.2.

```
What steps will reproduce the problem?
1. Connect a UART based GSM modem to AM18x kit running 'rowboat-android'.
2. Configure RIL flags in "/system/build.prop" to detect the modem.
3. Start RILD.

What is the expected output? What do you see instead?
Correct response to AT commands.

Output seen is:
D/AT ( 713): AT> ATE0Q0V1
D/AT ( 713): AT< OK
D/AT ( 713): AT> ATS0=0
D/AT ( 713): AT< OK
D/AT ( 713): AT> AT+CMEE=1
D/AT ( 713): AT< OK
D/AT ( 713): AT> AT+CREG=2
D/AT ( 713): atchannel: EOF reached
I/RIL ( 713): AT channel closed
D/RIL ( 713): onRequest: RADIO_POWER
D/RIL ( 713): onRequest: SCREEN_STATE
D/RILJ ( 857): [1587]< RADIO_POWER error:
com.android.internal.telephony.CommandException: GENERIC_FAILURE
D/RIL ( 713): onRequest: BASEBAND_VERSION
D/RILB ( 857): Notifying: radio not available

What version of the product are you using? On what operating system?
Android-2.2

Please provide any additional information below.
-
```

Original issue reported on code.google.com by `zaheer.m...@gmail.com` on 12 Feb 2011 at 1:36

Start by reviewing the RIL flags in /system/build.prop and the RILD startup path on the AM18x kit. Reproduce the UART modem sequence and inspect the AT channel around AT+CREG=2, where the log reports EOF and the channel closes. Done means RILD receives the expected AT responses without RADIO_POWER failing or the radio becoming unavailable.

Written by the indexing model from the issue text.