fix: warning: ISO C++ forbids converting a string constant to char*

Signed-off-by: Oleg Kokorin <[email protected]>

Author: Ole2mail

connectivity/cellular/include/cellular/framework/AT/AT_CellularDevice.h

@@ -67,7 +67,7 @@ class AT_CellularDevice : public CellularDevice {
     };
 
 public:
-    AT_CellularDevice(FileHandle *fh, char *delim = "\r");
+    AT_CellularDevice(FileHandle *fh, const char *delim = "\r");
     virtual ~AT_CellularDevice();
 
     virtual nsapi_error_t clear();

connectivity/cellular/source/framework/AT/AT_CellularDevice.cpp

@@ -39,7 +39,7 @@ using namespace std::chrono_literals;
 #define DEFAULT_AT_TIMEOUT 1s // at default timeout
 const int MAX_SIM_RESPONSE_LENGTH = 16;
 
-AT_CellularDevice::AT_CellularDevice(FileHandle *fh, char *delim):
+AT_CellularDevice::AT_CellularDevice(FileHandle *fh, const char *delim):
     CellularDevice(),
     _at(fh, _queue, DEFAULT_AT_TIMEOUT, delim),
 #if MBED_CONF_CELLULAR_USE_SMS