[rilmodem] Enable SIM operations in expired SIM cards

Following Android example for interpreting RIL_APPSTATE_ILLEGAL
as RIL_APPSTATE_READY. E.g. SIM cards that are expired can go to
this state. By mapping the state to READY we are still able to
use the SIM features such as reading phonebook. Network access
will not be permitted with such SIM card regardless or READY
state.

Signed-off-by: Miia Leinonen <miia.leinonen@oss.tieto.com>