uml: console driver cleanups

Console driver cleanups -
	Changed an instance of foo = bar + foo to foo += bar
	Removed checks of tty->stopped - I don't think the low-level
driver has any business looking at that
	Removed an annoying warning

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>