xhci: dbgtty: remove kfifo_out() wrapper

xhci: dbgtty: remove kfifo_out() wrapper

There is no need to check against kfifo_len() before kfifo_out(). Just
ask the latter for data and it tells how much it retrieved. Or returns 0
in case there are no more.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Mathias Nyman <mathias.nyman@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org
Link: https://lore.kernel.org/r/20240808103549.429349-5-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>