drivers: modem: Add BG9X Kconfig dependency

The modem subsystem cannot be enabled for systems using the
'quectel,bg9x' driver. Fix it by adding
DT_HAS_QUECTEL_BG9X_ENABLED dependency to MODEM_CELLULAR
Kconfig option.

Signed-off-by: Guilherme Costa <guilhermecosta@stratioautomotive.com>

Author: guildeol-stra

drivers/modem/Kconfig.cellular

@@ -14,13 +14,13 @@ config MODEM_CELLULAR
 	select NET_L2_PPP_OPTION_MRU
 	select NET_L2_PPP_PAP
 	select NET_L2_PPP_MGMT
-	depends on (DT_HAS_QUECTEL_BG95_ENABLED || DT_HAS_SIMCOM_A76XX_ENABLED || \
-		    DT_HAS_SIMCOM_SIM7080_ENABLED || DT_HAS_U_BLOX_SARA_R4_ENABLED || \
-		    DT_HAS_U_BLOX_SARA_R5_ENABLED || DT_HAS_SWIR_HL7800_ENABLED || \
-		    DT_HAS_TELIT_ME910G1_ENABLED || DT_HAS_TELIT_ME310G1_ENABLED || \
-		    DT_HAS_QUECTEL_EG25_G_ENABLED || DT_HAS_NORDIC_NRF91_SLM_ENABLED || \
-		    DT_HAS_SQN_GM02S_ENABLED || DT_HAS_U_BLOX_LARA_R6_ENABLED || \
-		    DT_HAS_QUECTEL_EG800Q_ENABLED)
+	depends on (DT_HAS_QUECTEL_BG95_ENABLED || DT_HAS_QUECTEL_BG9X_ENABLED || \
+		    DT_HAS_SIMCOM_A76XX_ENABLED || DT_HAS_SIMCOM_SIM7080_ENABLED || \
+		    DT_HAS_U_BLOX_SARA_R4_ENABLED || DT_HAS_U_BLOX_SARA_R5_ENABLED || \
+		    DT_HAS_SWIR_HL7800_ENABLED || DT_HAS_TELIT_ME910G1_ENABLED || \
+		    DT_HAS_TELIT_ME310G1_ENABLED || DT_HAS_QUECTEL_EG25_G_ENABLED || \
+		    DT_HAS_NORDIC_NRF91_SLM_ENABLED || DT_HAS_SQN_GM02S_ENABLED || \
+		    DT_HAS_U_BLOX_LARA_R6_ENABLED || DT_HAS_QUECTEL_EG800Q_ENABLED)
 	help
 	  This driver uses the generic 3gpp AT commands, along
 	  with the standard protocols CMUX and PPP, to configure