Prepare the Renode models for changing the PeripheralRegister underlying type

As the `PeripheralRegister` underlying value type is about to change from `ulong` to `uint` all models have to be adjusted accordingly.
This change is compatible with both the upcoming change and with the current master/nightly.

Change-Id: I7422ae92a2767288cbc899602a8a3b7a45080f3c

shodan_infrastructure/DoubleBufferDMA.cs

diff --git a/shodan_infrastructure/DoubleBufferDMA.cs b/shodan_infrastructure/DoubleBufferDMA.cs
index 4034335..8f41019 100644
--- a/shodan_infrastructure/DoubleBufferDMA.cs
+++ b/shodan_infrastructure/DoubleBufferDMA.cs
@@ -58,7 +58,7 @@
             // Restore bottom 3 bits of address.
             var addr1 = rxBuffer1Address.Value << 3;
 
-            if(data.Length != size)
+            if((ulong)data.Length != size)
             {
                 this.Log(LogLevel.Warning, "Received {0} bytes from the device, but RX DMA stream is configured for {1} bytes. This might indicate problems in the driver", data.Length, size);
             }

shodan_infrastructure/SpringbokRiscV32.cs

diff --git a/shodan_infrastructure/SpringbokRiscV32.cs b/shodan_infrastructure/SpringbokRiscV32.cs
index b7a5c08..cc52b19 100644
--- a/shodan_infrastructure/SpringbokRiscV32.cs
+++ b/shodan_infrastructure/SpringbokRiscV32.cs
@@ -340,11 +340,12 @@
                   // If valid, do the memory clear.
                   if (val)
                         {
+                            var dataPageMask = ~((ulong)(DataPageSize - 1));
                             InitStatusPending.Value = true;
                             InitStatusDone.Value = false;
                             Machine.LocalTimeSource.ExecuteInNearestSyncedState( __ => {
-                                for(long writeAddress = InitStartAddress.Value & ~(DataPageSize - 1);
-                                    writeAddress < ((InitEndAddress.Value + DataPageSize - 1) & ~(DataPageSize - 1));
+                                for(ulong writeAddress = InitStartAddress.Value & dataPageMask;
+                                    writeAddress < ((InitEndAddress.Value + DataPageSize - 1) & dataPageMask);
                                     writeAddress += DataPageSize)
                                 {
                                     Machine.SystemBus.WriteBytes(DataErasePattern, mmuRangeStart + (ulong)writeAddress, (uint)DataPageSize, true);