Fixes RP2040 buffer reallocation overrun problem

[ndinsmore]

Describe the PR
This is a simple fix for the rp2040 device that prevents drives that open and close an ep (ie. audio device) from reallocating the buffer in the DPRAM and running out of space and failing the assert.

This should close:
#628
raspberrypi/pico-sdk/issues/85

Additional context
If applicable, add any other context about the PR and/or screenshots here.

[liamfraser]

Looks like a plausible fix to me. I think the audio example may be the first one that repeatedly opens and closes an ep which is why we didn't see this?

[liamfraser]

This looks good, but there is a larger issue here that we don't implement dcd_edpt_close. However, in this instance I feel that closing and opening the endpoint all the time is inefficient so this fix is good enough. Longer term I will raise an issue to implement dcd_edpt_close

[hathach]

This looks good, but there is a larger issue here that we don't implement dcd_edpt_close. However, in this instance I feel that closing and opening the endpoint all the time is inefficient so this fix is good enough. Longer term I will raise an issue to implement dcd_edpt_close

Thanks for reviewing, feel free to merge it when you think it is ready.