drivers: rf-transceiver: ad9361: fix icp_val exceeding 6 bits

[Xenoamor]

Pull Request Description

Currently the icp_val is clamped to 64. This is 7 bits and bleeds into the "Must be 0" section violating the datasheet, this change clamps it correctly to 63

PR Type

• Bug fix (change that fixes an issue)
• New feature (change that adds new functionality)
• Breaking change (has dependencies in other repos or will cause CI to fail)

PR Checklist

• I have followed the Coding style guidelines
• I have complied with the Submission Checklist
• I have performed a self-review of the changes
• I have commented my code, at least hard-to-understand parts
• I have build all projects affected by the changes in this PR
• I have tested in hardware affected projects, at the relevant boards
• I have signed off all commits from this PR
• I have updated the documentation (wiki pages, ReadMe etc), if applies

[CLAassistant]

All committers have signed the CLA.