To be compatible with the previous method, add a buf between cdcacm
and serial. Because when using usbreqbuf directly as the buf of serial,
the amount of data received may be insufficient due to the limit of the
number of reqs. For example, when the number of reqs is 4, the number
of data received through cdcacm is 5, and each data is a separate USB
packet, which should require 5 reqs, resulting in the last number not
being received. If the application always waits for 5 numbers before
performing an operation, this will cause problems.
Signed-off-by: yangsong8 <yangsong8@xiaomi.com>
f0b52a8b2d