x86, um: get rid of system.h -> system.h include

Long-term we want to split system.h and include barriers part from
underlying target; for now copy that part to sysdep.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
7 files changed