CVE-2023-53840

In the Linux kernel, the following vulnerability has been resolved:

usb: early: xhci-dbc: Fix a potential out-of-bound memory access

If xdbc_bulk_write() fails, the values in 'buf' can be anything. So the
string is not guaranteed to be NULL terminated when xdbc_trace() is called.

Reserve an extra byte, which will be zeroed automatically because 'buf' is
a static variable, in order to avoid troubles, should it happen.