Potential data overwrite when reading in chucks

[urbytes21]

Thank you for this great library. I’ve been using it and customizing it for my CDC Host application.

I noticed an issue in the read() API here:

USBHostSerial/src/USBHostSerial.cpp

Line 124 in 43a396f

std::memcpy(dest, ret, pxItemSize);

When reading data in multiple chunks from the ring buffer, memcpy always copies into dest without advancing the destination pointer. This overwrites previously read data.

I will push a PR for this. Please help me review. @bertmelis

Thank you.

[bertmelis]

Fixed with #20