NRF52840: enabled SdBlockDevice capability

[kegilbert]

NOTE This is a duplicate PR of #4478. There was a merge conflict after some recent changes were pushed up to master. I used the GitHub fix conflicts shiny button which created a merge commit. I wasn't able to undo it in a clean way, so I moved the rebase to this branch.

---

Rebase against master for: #4088

Smaller chunk of the Workshop branch additions: #4412

Feel free to add in however else should be a reviewer @c1728p9

Changes from the original commit to targets/TARGET_NORDIC/TARGET_NRF5_SDK13/spi_api.c have been removed as the following commit removed those files as orphans:
708dd47

[studavekar]

/morph test

[kegilbert]

NUCLEO_F429ZI-ARM.tests-mbed_drivers-flashiap.FlashIAP - program
NUCLEO_F429ZI-ARM.tests-mbed_hal-flash.Flash - erase sector

Both failed with any compiler (http://mbed-ci-master-2.austin.arm.com:8081/job/test_matrix/475/)

Affected targets:
NUCLEO_F429ZI
UBLOX_EVK_ODIN_W2

Have a second test run kicked off to confirm, but seeing as this is a flash API rework on the above two targets I'm inclined to believe the results for now. Wasn't able to run the test locally at the moment, does anyone more familiar with the original change have any insight?

The tests in question:
https://github.com/ARMmbed/mbed-os/blob/master/TESTS/mbed_drivers/flashiap/main.cpp
https://github.com/ARMmbed/mbed-os/blob/master/TESTS/mbed_hal/flash/functional_tests/main.cpp

CC @nvlsianpu

[mbed-bot]

Result: SUCCESS

Your command has finished executing! Here's what you wrote!

/morph test

Output

mbed Build Number: 511

All builds and test passed!

[0xc0170]

@nvlsianpu happy with this rebased patch?

@kegilbert I dont fully understand the above, I cant spot any failures here and those devices are not even touched here.

[nvlsianpu]

looks good