Fixed Serial ambiguity for enable_input and enable_output

[pgasiorMobica]

Summary of changes

Fixes regarding issue #12107. There was an ambiguity of enable_input and enable_output functions in the Serial API class from SerialBase and FileHandle. This was fixed by adding using to the Serial.h class declaration:

using SerialBase::enable_input;
using SerialBase::enable_output;

Impact of changes

Migration actions required

Documentation

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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

Compile errors eliminated.

[] 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

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Reviewers

@paul-szczepanek-arm

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[ciarmcom]

@pgasiorMobica, thank you for your changes.
@paul-szczepanek-arm @ARMmbed/mbed-os-core @ARMmbed/mbed-os-maintainers please review.

[kjbracey]

CI started

[mbed-ci]

Test run: SUCCESS

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