Cypress: Update WHD to version 1.91.2

[kyle-cypress]

Summary of changes

Update WHD to version 1.91.2. Fixes incorrect security type reported by scan in some cases.

Impact of changes

NA

Migration actions required

NA

Documentation

NA

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Pull request type

[x] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

[] No Tests required for this change (E.g docs only update)
[] Covered by existing mbed-os tests (Greentea or Unittest)
[x] Tests / results supplied as part of this PR

GT_FT_P6S1_43012EVB_01_GCC_NET.txt
GT_FT_P6S1_43438EVB_01_GCC_NET.txt
GT_FT_PROTO_062S3_4343W_GCC_NET.txt
GT-FT-KIT_062_WIFI_BT-GCC-NET.txt
GT-FT-KIT-062S2-43012-GCC-NET.txt
GT-FT-PROT-062-4343W-GCC-NET.txt

The wifi-scan failures are an internal test infrastructure issue.
The failures of tests-integration-fs-single and tests-netsocket-tls are transient.
All of the above passed when re-run manually.

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Reviewers

@ARMmbed/team-cypress

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[ciarmcom]

@kyle-cypress, thank you for your changes.
@maclobdell @ARMmbed/mbed-os-ipcore @ARMmbed/mbed-os-maintainers please review.

[0xc0170]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 6 of 6 test jobs passed
Build number : 1
Build artifacts

[mergify]

This PR does not contain release version label after merging.