[RILMODEM] gprs set detach notified only for callback

Signed-off-by: Jarko Poutiainen <Jarko.Poutiainen@oss.tieto.com>
[rilmodem] Don't send <CR> with USSD string
Merge pull request #232 from mkuukkane/ussd

[rilmodem] Don't send <CR> with USSD string
Merge pull request #231 from jpoutiai/gprs

[RILMODEM] gprs set detach notified only for callback