xhci: dbgtty: Improve performance by handling received data immediately.

xhci: dbgtty: Improve performance by handling received data immediately.

Improve dbc transfer rate performance by copying the received data to
the tty buffer directly in the request complete callback function if
possible.
Only defer it in case there is already pending deferred work, tty is
throttled, or we fail copy the data to the tty buffer

The request complete callback is already called by a workqueue.

This is part 3/3 of a dbc performance improvement series that roughly
triples dbc performace when using adb push and pull over dbc.

Max/min push rate after patches is 210/118 MB/s, pull rate 171/133 MB/s,
tested with large files (300MB-9GB) by Łukasz Bartosik

Cc: Łukasz Bartosik <ukaszb@chromium.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20241227120142.1035206-3-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>