[PATCH] Split out screen_info from tty.h

This makes it possible for boot code to use screen_info without dragging in
all of tty.h.

Signed-off-by: Brian Gerst <bgerst@didntduck.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>