drivers: modem: wncm14a2a: Convert driver to new DT device macros

Convert wncm14a2a driver:

    NET_DEVICE_OFFLOAD_INIT -> NET_DEVICE_DT_INST_OFFLOAD_DEFINE

Signed-off-by: Marcin Niestroj <m.niestroj@grinn-global.com>
diff --git a/drivers/modem/wncm14a2a.c b/drivers/modem/wncm14a2a.c
index 293eb31..5140010 100644
--- a/drivers/modem/wncm14a2a.c
+++ b/drivers/modem/wncm14a2a.c
@@ -1848,7 +1848,8 @@
 	.init	= offload_iface_init,
 };
 
-NET_DEVICE_OFFLOAD_INIT(modem_wncm14a2a, "MODEM_WNCM14A2A",
-			wncm14a2a_init, device_pm_control_nop, &ictx,
-			NULL, CONFIG_MODEM_WNCM14A2A_INIT_PRIORITY, &api_funcs,
-			MDM_MAX_DATA_LENGTH);
+NET_DEVICE_DT_INST_OFFLOAD_DEFINE(0, wncm14a2a_init, device_pm_control_nop,
+				  &ictx, NULL,
+				  CONFIG_MODEM_WNCM14A2A_INIT_PRIORITY,
+				  &api_funcs,
+				  MDM_MAX_DATA_LENGTH);