USB: tty: Prune uses of tty_request_room in the USB layer

We have lots of callers that do not need to do this in the first place.
Remove the calls as they both cost CPU and for big buffers can mess up the
multi-page allocation avoidance.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>