PDP Type needs to be IPV4V6

1.Testing with Verizon and AT&T SIMs, PDP type is automatically set to IPV4V6.
2. Testing with AT&T IoT SIM, PDP type automatically sets to IP. It will connect
but not communicate. Setting a subsequent APN to IPV4V6 with the same APN communicates.

features/cellular/framework/targets/MultiTech/DragonflyNano/PPP/SARA4_PPP.cpp

@@ -32,9 +32,9 @@ static const intptr_t cellular_properties[AT_CellularDevice::PROPERTY_MAX] = {
     1,  // AT_CSMP
     1,  // AT_CMGF
     1,  // AT_CSDH
-    1,  // PROPERTY_IPV4_STACK
+    0,  // PROPERTY_IPV4_STACK
     0,  // PROPERTY_IPV6_STACK
-    0,  // PROPERTY_IPV4V6_STACK
+    1,  // PROPERTY_IPV4V6_STACK
     0,  // PROPERTY_NON_IP_PDP_TYPE
     1,  // PROPERTY_AT_CGEREP
     1,  // PROPERTY_AT_COPS_FALLBACK_AUTO