Fix renode error

Change-Id: I692934aef3d3e325a30d268651c2eb8e0017d597

shodan_infrastructure/SpringbokRiscV32.cs

diff --git a/shodan_infrastructure/SpringbokRiscV32.cs b/shodan_infrastructure/SpringbokRiscV32.cs
index bef2b2f..bc52a4e 100644
--- a/shodan_infrastructure/SpringbokRiscV32.cs
+++ b/shodan_infrastructure/SpringbokRiscV32.cs
@@ -184,8 +184,8 @@
             // do not validate rw bit as VexRiscv custom CSRs do not follow the standard
             CSRValidation = CSRValidationLevel.None;
 
-            RegisterCSR((ulong)CSRs.InstructionCount, () => InstructionCountCSRRead("InstructionCount"), value => { });
-            RegisterCSR((ulong)CSRs.CycleCount, () => InstructionCountCSRRead("CycleCount"), value => { });
+            RegisterCSR((ushort)CSRs.InstructionCount, () => InstructionCountCSRRead("InstructionCount"), value => { });
+            RegisterCSR((ushort)CSRs.CycleCount, () => InstructionCountCSRRead("CycleCount"), value => { });
         }
 
         private ulong InstructionCountCSRRead(string name)