Bug 1009393 - [B2G][Emulator] support RIL_REQUEST_CDMA_FLASH

Use AT+WFSH. The command isn't defined in TS 27.007 but I learned that
it's kinda de-facto. Please see [1].
[1] http://www.multitech.com/en_us/documents/collateral/manuals/s000294l.pdf