Kinetis USB improvements and fixes

[c1728p9]

Make the following improvements and fixes:

1. Update the Kinetis USB driver so that endpointReadResult only reads the result of the last read and does not trigger a new read. Instead move the code to trigger new reads into endpointRead.
2. Fix the race condition in controlIn caused by a call to EP0read() followed immediately by EP0readStage(). This is done by setting up to read the next setup packet (ignoring the status stage)
   in endpointReadResult rather than in EP0readStage. This makes the function EP0readStage unnecissary.
3. Remove the Kinetis workaround in controlOut in USBDevice.cpp since point 2 fixes this bug. For more info on this see the PR which added this workaround - Fix KL25Z connect problem with some USB 3.0 hosts #414

[c1728p9]

@Sissors in theory this should fix the USB stability problems on the K64F. Please test (you'll need to move USBDevice out of the unsupported folder) and let me know if this fixes the issues you were seeing. I tried your ram disk example from #4761, but couldn't reproduce your failure - it worked both before and after this change. When building in debug mode I did get Mutex 0x20003c84 error -6: Not allowed in ISR context but this was fixed by either building as release or pulling in the changes in #5874 (specifically commit Fix local static initialization in USB).

CC @mjrgh @larsgk @0xc0170 @Sissors @mmahadevan108 @ashok-rao

[c1728p9]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 891
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/5877/

Triggering tests

/morph test
/morph uvisor-test
/morph export-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 564
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/5877/

[mbed-ci]

Test : SUCCESS

Build number : 736
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/5877/736

[Sissors]

Didn't see the comment in my mailbox between all build related mails ;). I will try it one of the coming days to see if it solves those issues.