Fix TDBStore sizes for SecureStore tests

[SeppoTakalo]

Summary of changes

Tests must require at least 2 erase sectors per TDBStore,
so that the garbage collection may work.

Fixes #12031

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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

[0xc0170]

@SeppoTakalo I set this to 5.15rc2 (as PR #11918 is in that release as well causing the issue referenced and fixed here).

[0xc0170]

CI started

[SeppoTakalo]

This cannot be applied to 5.15 branch. Base file is different.

Some changes have been marked as feature changes and therefore did not go into 5.15 branch.
I need to provide separate patch for 5.15.

[SeppoTakalo]

Actually, this applies cleanly if 0fe159f is also applied to 5.15 before this one.

[SeppoTakalo]

@0xc0170 and @adbridge Please note, for 5.15 you need to cherry-pick
0fe159f
before applying this patch.

The mentioned patch was part of bigger PR that cannot be brought into 5.15 fully, so just apply that one commit from there.

[adbridge]

@0xc0170 this is only a change to tests why have you tagged Cypress for review ?

[SeppoTakalo]

@adbridge
Original issue was reported by Cypress on one of their board.

[VeijoPesonen]

Looks good to me

[mbed-ci]

Test run: FAILED

Summary: 1 of 5 test jobs failed
Build number : 1
Build artifacts

Failed test jobs:

• jenkins-ci/mbed-os-ci_greentea-test

[0xc0170]

Removed the release label, there is #12056 that will go to the release 5.15 branch

[SeppoTakalo]

@0xc0170 both should be included in the 5.15.

The #12056 fixes one test, and is required so that this PR can be applied cleanly.

[adbridge]

@SeppoTakalo are you saying that this PR also should go to 5.15 as well as #12056 ?