fix: ssrdp.yaml file reference in mop.r.n.yaml (#1066)

Fixes: #1065 

Fix incorrect file reference in mop.r.n.yaml hints section

## Problem
The `mop.r.n.yaml` file contains an incorrect file reference in its
hints section that points to a non-existent file path:

## Solution
it should point to Zicfiss,

hints:
```yaml
  - { $ref: inst/Zicfiss/ssrdp.yaml# }  # Correct path fixed
```

- Also added validation check , Method: Udb::Instruction#validate
- Tests each $ref by dereferencing it 
- Prevents future broken hint references

Ready for Review sir @ThinkOpenly sir @dhower-qc

---------

Signed-off-by: Sukuna0007Abhi <[email protected]>

Author: Sukuna0007Abhi

spec/std/isa/inst/Zimop/mop.r.n.yaml

@@ -30,7 +30,7 @@ data_independent_timing: false
 hints:
   - { $ref: inst/Zicfilp/sspopchk.x1.yaml# }
   - { $ref: inst/Zicfilp/sspopchk.x5.yaml# }
-  - { $ref: inst/Zicfilp/ssrdp.yaml# }
+  - { $ref: inst/Zicfiss/ssrdp.yaml# }
 pseudoinstructions:
   - when: n == 0
     to: mop.r.0

tools/ruby-gems/udb/lib/udb/obj/instruction.rb

@@ -327,6 +327,23 @@ def validate(resolver)
         Instruction.deprecated_validate_encoding(@data["encoding"]["RV64"], name)
       end
     end
+
+    # Validate hint references
+    if @data.key?("hints")
+      @data["hints"].each_with_index do |hint, index|
+        if hint.key?("$ref")
+          begin
+            # Try to dereference the hint to validate it exists
+            hint_inst = @cfg_arch.ref(hint["$ref"])
+            if hint_inst.nil?
+              raise "Invalid hint reference in instruction '#{name}' at hints[#{index}]: '#{hint["$ref"]}' - reference not found"
+            end
+          rescue => e
+            raise "Invalid hint reference in instruction '#{name}' at hints[#{index}]: '#{hint["$ref"]}' - #{e.message}"
+          end
+        end
+      end
+    end
   end
 
   def ==(other)