drivers: modem_cellular: Add shutdown script for BG95

Add quectel_bg95_shutdown_chat_script that issues AT+QPOWD=1 and
link it to MODEM_CELLULAR_DEVICE_QUECTEL_BG95 to enable a clean
software-initiated power-off path

Signed-off-by: Van Petrosyan <van.petrosyan@sensirion.com>

Author: petrosyan-van

drivers/modem/modem_cellular.c

@@ -1986,6 +1986,13 @@ MODEM_CHAT_SCRIPT_CMDS_DEFINE(quectel_bg95_periodic_chat_script_cmds,
 MODEM_CHAT_SCRIPT_DEFINE(quectel_bg95_periodic_chat_script,
 			 quectel_bg95_periodic_chat_script_cmds, abort_matches,
 			 modem_cellular_chat_callback_handler, 4);
+
+MODEM_CHAT_SCRIPT_CMDS_DEFINE(quectel_bg95_shutdown_chat_script_cmds,
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+QPOWD=1", ok_match));
+
+MODEM_CHAT_SCRIPT_DEFINE(quectel_bg95_shutdown_chat_script,
+			 quectel_bg95_shutdown_chat_script_cmds, abort_matches,
+			 modem_cellular_chat_callback_handler, 10);
 #endif
 
 #if DT_HAS_COMPAT_STATUS_OKAY(quectel_eg25_g)
@@ -2669,7 +2676,8 @@ MODEM_CHAT_SCRIPT_DEFINE(sqn_gm02s_periodic_chat_script,
 				       NULL,                                                       \
 				       &quectel_bg95_init_chat_script,                             \
 				       &quectel_bg95_dial_chat_script,                             \
-				       &quectel_bg95_periodic_chat_script, NULL)
+				       &quectel_bg95_periodic_chat_script,                         \
+				       &quectel_bg95_shutdown_chat_script)
 
 #define MODEM_CELLULAR_DEVICE_QUECTEL_EG25_G(inst)                                                 \
 	MODEM_PPP_DEFINE(MODEM_CELLULAR_INST_NAME(ppp, inst), NULL, 98, 1500, 64);                 \