add sfp get error description (#13275)

Why I did it
Command "sudo sfputil show error-status -hw" shows "OK (Not implemented)" in the output.

How I did it
Add a new SFP API get_error_description support in Nokia sonic-platform sfp.py module.

How to verify it
Run the new image and execute command "sudo sfputil show error-status -hw"

platform/marvell-armhf/sonic-platform-nokia/7215/sonic_platform/sfp.py

@@ -969,3 +969,20 @@ class Sfp(SfpBase):
             integer: The 1-based relative physical position in parent device
         """
         return self.index
+    
+    def get_error_description(self):
+        """
+        Retrives the error descriptions of the SFP module
+
+        Returns:
+            String that represents the current error descriptions of vendor specific errors
+            In case there are multiple errors, they should be joined by '|',
+            like: "Bad EEPROM|Unsupported cable"
+        """
+        
+        if not self.get_presence():
+            error_description = self.SFP_STATUS_UNPLUGGED
+        else:
+            error_description = self.SFP_STATUS_OK
+
+        return error_description