Add RSSI member into gsm_ppp_modem_info structure in order to
get that information using the gsm_ppp_modem_info function.
Signed-off-by: Bartosz Bilas <b.bilas@grinn-global.com>
Make modem_info structure public in order to allow the user
to get modem information using gsm_ppp_modem_info function.
Move modem info query commands into separate function
that's called only once during gsm configuring because
there is no necessity to re-querying modem since
they should not change.
Signed-off-by: Bartosz Bilas <b.bilas@grinn-global.com>