Minimal Console: Fix syntax errors

[hugueskamba]

Description

Summary of change

Fix syntax error that prevent building when "platform.stdio-minimal-console-only" is true.

Documentation

---

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)

---

Test results

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

See: #11796 (comment)

---

Reviewers

@evedon @rajkan01

---

Release Notes

Summary of changes

Impact of changes

Migration actions required

[0xc0170]

No nightly failures for these?

[0xc0170]

CI started

[0xc0170]

Set to 5.15 as it fixing the feature there.

[hugueskamba]

No nightly failures for these?

No because the parameter is false by default. See details in this PR description what was agreed to be done in terms of testing.

[mbed-ci]

Test run: FAILED

Summary: 1 of 11 test jobs failed
Build number : 1
Build artifacts

Failed test jobs:

• jenkins-ci/mbed-os-ci_greentea-test

[0xc0170]

Test restarted

[0xc0170]

CI restarted