Setting K64F to use KVStore FileSystem configuration

[yossi2le]

Description

This PR change the default KVStore configuration of K64F to FILESYSTEM means, that KVStore will work over filesystem using the FileSystemStore implementation and SecureStore implementation.
Previously PR has changed it to TDB_INTERNAL, which was a mistake.

Pull request type

[ x ] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

[0xc0170]

Travis failure will be fixed on master soon (we will request rebase once done). See #8945

[0xc0170]

Travis failure will be fixed on master soon (we will request rebase once done). See #8945

The fix is on master, if you rebase, it should allow travis to run

[cmonr]

@yossi2le What's the difference between having storage_type set to TDB_INTERNAL vs FILESYSTEM?

[dannybenor]

@cmonr You can see the answer here https://github.com/ARMmbed/mbed-os-5-docs/blob/development/docs/reference/configuration/Storage.md#kvstore-configuration

[cmonr]

CI started

[cmonr]

@yossi2le @dannybenor PR looks fine to me, just wondering why the K64F would need a different config than the K66F. Is that because of the differenced between each eval board, and not just the chip family?

[dannybenor]

@cmonr It is more an issue of testing. K66F was selected by Pelion Client team to be the platform to test internal memory, while K64F is currently used with SD cards, and it is more suitable to test file system configuration.

[mbed-ci]

Test run: SUCCESS

Summary: 4 of 4 test jobs passed
Build number : 1
Build artifacts
Build logs

[0xc0170]

Test restarted, error not related to the change.

[0xc0170]

Test restarted