Enable asynchronous serial with DMA for K66F

[michalpasztamobica]

Description

Added DMA definitions and usage for UART, based on K64F's code.

We need this to improve the UART's performance when K66F interacts with ESP8266. We've seen a lot of missing packets and device errors reported in UDP tests. This change improves the situation significantly.

@0xc0170 , I'd be grateful if you could check if the license header in dma_reqs.h is fine? The file is copied over from K64F with a minor modification...

Pull request type

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

Reviewers

@SeppoTakalo
@AnttiKauppila
@VeijoPesonen

[ciarmcom]

@michalpasztamobica, thank you for your changes.
@maclobdell @AnttiKauppila @VeijoPesonen @SeppoTakalo @ARMmbed/mbed-os-maintainers please review.

[kjbracey]

Are you actually planning to use the asynchronous serlal? UARTSerial doesn't at present, but maybe there's some other fix here that helps it?

(There is a patch kicking around somewhere that experimentally makes it use asynchronous for TX. RX would be a trickier - not 100% sure it's feasible)

[kjbracey]

On the assumption that this is indeed copying the K64F code, approved, but should run it by the NXP guys. They would know if there are any important differences between the two chips.

[michalpasztamobica]

@kjbracey-arm , yes I copied the K64F code and removed UART5 (K66F only has UART0-4). The DMA callbacks were already declared, but not used, so I think this is safe.

@ARMmbed/team-nxp , your feedback will be very valuable :)

[0xc0170]

@mmahadevan108 Please review

[0xc0170]

can this be removed?

[mmahadevan108]

This feature is not complete and needs to be completed. We can leave it in for now and I will work to update this support to support CHARACTER_MATCH

[mmahadevan108]

@michalpasztamobica Thank you for the update

[0xc0170]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 1
Build artifacts