Extracted staffVolumeDown to seperate file

src/staffFunctions.cpp

@@ -1,5 +1,6 @@
 #include <staffFunctions.h>
 #include <constants.h>
+#include <potControlls.h>
 
 void staffVolumeUp(int *maxVolume)
 {
@@ -7,4 +8,28 @@ void staffVolumeUp(int *maxVolume)
     {
         *maxVolume += STAFF_STEPS;
     }
+}
+
+void staffVolumeDown(int maxVolume, int *userVolume, int *oldUserVolume)
+{
+    if (maxVolume > STAFF_STEPS)
+    {
+        maxVolume -= STAFF_STEPS;
+
+        if (*userVolume > maxVolume)
+        {
+            for (int i = 0; i < (*userVolume - maxVolume); i++)
+            {
+                potDecrement();
+            }
+
+            *userVolume = maxVolume;
+            *oldUserVolume = *userVolume;
+        }
+
+        if (*oldUserVolume > maxVolume)
+        {
+            *oldUserVolume = maxVolume;
+        }
+    }
 }