stm32h750-dk support

[antoniovazquezblanco]

Describe the PR
Add support for the aforementioned discovery kit.
See https://www.st.com/en/evaluation-tools/stm32h750b-dk.html#overview for more details about it.

Additional context
Initial support and tested a couple of example projects.
This is my first contribution to the project so please be patient.

Thanks

[hathach]

thank you for the PR, you are doing great, and it looks good. I just rebase and update the PR to match latest change. However, the board should use both startup and linker for h750, would you mind updating and testing it again. Thank you

[antoniovazquezblanco]

Currently contributing with a sample linker script that may suit our needs in STMicroelectronics/cmsis-device-h7#8

[hathach]

Currently contributing with a sample linker script that may suit our needs in STMicroelectronics/cmsis_device_h7#8

we don't need to wait for this, it would take forever for ST to merge this. Instead you could just copy the linker to the board folder and update the value correctly using BOARD_PATH like this board https://github.com/hathach/tinyusb/tree/master/hw/bsp/stm32h7/boards/daisyseed

[antoniovazquezblanco]

Done!

[hathach]

perfect, thank you for your hard works

[antoniovazquezblanco]

Thank you very much!