updated the use of x0 operand

[kumaransvyoma]

Description

Provide a detailed description of the changes performed by the PR.

Related Issues

Please list all the issues related to this PR. Use NA if no issues exist

Ratified/Unratified Extensions

• Ratified
• Unratified

List Extensions

List the extensions that your PR affects. In case of unratified extensions, please provide a link to the spec draft that was referred to make this PR.

Reference Model Used

• SAIL
• Spike
• Other - < SPECIFY HERE >

Mandatory Checklist:

• All tests are compliant with the test-format spec present in this repo ?
• Ran the new tests on RISCOF with SAIL/Spike as reference model successfully ?
• Ran the new tests on RISCOF in coverage mode
• Link to Google-Drive folder containing the new coverage reports (See this for more info): < SPECIFY HERE >
• Link to PR in RISCV-ISAC from which the reports were generated : < SPECIFY HERE >
• Changelog entry created with a minor patch

Optional Checklist:

• RISCV-V CTG PR link if tests were generated using it : < SPECIFY HERE >
• Were the tests hand-written/modified ?
• Have you run these on any hard DUT model ? Please specify name and provide link if possible in the description
• If you have modified arch_test.h Please provide a detailed description of the changes in the Description section above.