samples: cellular: lwm2m_carrier: Use LTE LC configs for PDN

The lwm2m_carrier sample uses the Link Controller library for PDN
handling. The SoftBank overlay was not updated when the PDN library was
deprecated, update it to align with the rest of the sample

Signed-off-by: Markus Rekdal <markus.rekdal@nordicsemi.no>

Author: nordic-mare

samples/cellular/lwm2m_carrier/overlay-softbank.conf

@@ -9,8 +9,8 @@ CONFIG_LWM2M_CARRIER_SOFTBANK=y
 CONFIG_LWM2M_CARRIER_SOFTBANK_DIVIDED_FOTA=y
 
 # Override default PDP context
-CONFIG_PDN_DEFAULTS_OVERRIDE=y
-CONFIG_PDN_DEFAULT_FAM_NONIP=y
+CONFIG_LTE_LC_PDN_DEFAULTS_OVERRIDE=y
+CONFIG_LTE_LC_PDN_DEFAULT_FAM_NONIP=y
 
 # Set NB-IoT system mode
 CONFIG_LTE_NETWORK_MODE_NBIOT=y