CellularStack: remove unnecessary assignment.

Fixes Coverity issue about unused variable.

Author: Tharazi97

features/cellular/framework/targets/RiotMicro/AT/RM1000_AT_CellularStack.cpp

@@ -281,10 +281,9 @@ nsapi_size_or_error_t RM1000_AT_CellularStack::socket_recvfrom_impl(CellularSock
         } else {
             if (count == 0) {
                 // Timeout with nothing received
-                nsapi_error_size = NSAPI_ERROR_WOULD_BLOCK;
                 success = false;
             }
-            size = 0; // This simply to cause an exit
+            break;
         }
     }
     timer.stop();

features/cellular/framework/targets/UBLOX/AT/UBLOX_AT_CellularStack.cpp

@@ -302,10 +302,9 @@ nsapi_size_or_error_t UBLOX_AT_CellularStack::socket_recvfrom_impl(CellularSocke
             } else {
                 if (count == 0) {
                     // Timeout with nothing received
-                    nsapi_error_size = NSAPI_ERROR_WOULD_BLOCK;
                     success = false;
                 }
-                size = 0; // This simply to cause an exit
+                break;
             }
         }
     } else if (socket->proto == NSAPI_TCP) {
@@ -346,10 +345,9 @@ nsapi_size_or_error_t UBLOX_AT_CellularStack::socket_recvfrom_impl(CellularSocke
             } else {
                 if (count == 0) {
                     // Timeout with nothing received
-                    nsapi_error_size = NSAPI_ERROR_WOULD_BLOCK;
                     success = false;
                 }
-                size = 0; // This simply to cause an exit
+                break;
             }
         }
     }