The recent change in bcbdee2357 means that
TinyUSB can no longer be run from within a soft (or hard) IRQ handler, ie
when the scheduler is locked. That means that Python code that calls
`print(...)` from within a scheduled function may block indefinitely if the
USB CDC buffers are full.
This commit fixes that problem by explicitly running the TinyUSB stack when
waiting within stdio tx/rx functions.
Signed-off-by: Damien George <damien@micropython.org>
a00c9d56db