Cellular: Remove friend definitions from cellular state machine

Instead of defining which classes can access state machine, CellularStateMachine
class is now "a normal" CPP class with public API.

Author: Kimmo Vaisanen

features/cellular/framework/device/CellularStateMachine.h

@@ -31,11 +31,9 @@ class CellularDevice;
  *  Finite State Machine for attaching to cellular network. Used by CellularDevice.
  */
 class CellularStateMachine {
-private:
-    // friend of CellularDevice so that it's the only way to close/delete this class.
-    friend class CellularDevice;
-    friend class AT_CellularDevice;
+public:
     friend class UT_CellularStateMachine; // for unit tests
+
     /** Constructor
      *
      * @param device    reference to CellularDevice
@@ -128,8 +126,21 @@ class CellularStateMachine {
     /** Reset the state machine to init state. After reset state machine can be used again to run to wanted state.
      */
     void reset();
-private:
+
+    /** Get retry timeout array
+     *
+     * @param timeout   Pointer to timeout array
+     * @param array_len Max lenght of the array
+     */
     void get_retry_timeout_array(uint16_t *timeout, int &array_len) const;
+
+    /** Change all cellular state timeouts
+     *
+     * @param timeout Timeout value (milliseconds)
+     */
+    void set_timeout(int timeout);
+
+private:
     bool power_on();
     bool open_sim();
     bool get_network_registration(CellularNetwork::RegistrationType type, CellularNetwork::RegistrationStatus &status, bool &is_registered);
@@ -188,8 +199,7 @@ class CellularStateMachine {
     int _state_timeout_registration;
     int _state_timeout_network;
     int _state_timeout_connect; // timeout for PS attach, PDN connect and socket operations
-    // Change all cellular state timeouts to `timeout`
-    void set_timeout(int timeout);
+
     cell_signal_quality_t _signal_quality;
 };