[nrf fromlist] drivers: modem_cellular: Update nRF91 Serial Modem PPP script

nRF91 Serial Modem application does not anymore start PPP automatically.
Update initialization script to request it.

Upstream PR #: 98788

Signed-off-by: Seppo Takalo <[email protected]>

Author: SeppoTakalo

drivers/modem/modem_cellular.c

@@ -2816,6 +2816,7 @@ MODEM_CHAT_SCRIPT_DEFINE(telit_me310g1_shutdown_chat_script,
 #if DT_HAS_COMPAT_STATUS_OKAY(nordic_nrf91_slm)
 MODEM_CHAT_SCRIPT_CMDS_DEFINE(nordic_nrf91_slm_init_chat_script_cmds,
 			      MODEM_CHAT_SCRIPT_CMD_RESP_MULT("AT", allow_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CFUN=4", ok_match),
 			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CMEE=1", ok_match),
 			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CEREG=1", ok_match),
 			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CEREG?", ok_match),
@@ -2833,7 +2834,7 @@ MODEM_CHAT_SCRIPT_DEFINE(nordic_nrf91_slm_init_chat_script, nordic_nrf91_slm_ini
 			 abort_matches, modem_cellular_chat_callback_handler, 10);
 
 MODEM_CHAT_SCRIPT_CMDS_DEFINE(nordic_nrf91_slm_dial_chat_script_cmds,
-			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CFUN=4", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT#XPPP=1", ok_match),
 			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CFUN=1", ok_match),
 			      MODEM_CHAT_SCRIPT_CMD_RESP("AT#XCMUX=2", ok_match));