cordio nrf: Add timer shutdown after time stop on deinit

[BramdeBoer1]

Summary of changes

This is a fix for issue #12127
This pull requests decreases the power consumption by 20uA after ble shutdown on the nrf52840 when using the cordio stack.

This is a recreated PR from #12136

Impact of changes

Migration actions required

Documentation

None

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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)
[X] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

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Reviewers

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[0xc0170]

Glad to see this again but I can't even tell why Travis has not yet started again 😭 I'll try to cherry pick this fix and recreate, will take over if I manage to get this running.

[0xc0170]

#12243 - Travis already in progress there. WIll continue there.