uml: tidy recently-moved code

uml: tidy recently-moved code

Now that the generic console operations are in a userspace file, we
can do the following:
	directly call into libc instead of through the os_* wrappers
	eliminate os_window_size since it has only one user

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>