Followed these steps to pass the parameters from main report to sub report
1. Create a new paramter @mainParam in the main report by right-clicking on 'Parameter Fields' section in Field explorer in the main report.
2. Create a new parameter @subParam in the sub report in the same manner (This wouldn't be required if you already have the parameter in the sub report)
3. Right click on the sub report in the desing window in your main report.
You will be able to see an option 'Change Subreport Links'.
4. Click on the option and select the @mainParam and transfer it to the sub report using '>' button.
5. Select the appropriate field in the sub report to map to
6. Click ok.
Now the field will be appearing only once in the criteria