x86, um: untangle uml ldt.h

* turn asm/ldt.h into ldt.h; update the (very few) users
* take host_ldt.h into sysdep, kill symlink mess
* includes of asm/arch/ldt.h turn into asm/ldt.h now

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/um/include/shared/sysdep-i386/tls.h b/arch/um/include/shared/sysdep-i386/tls.h
index 918fd3c..3455075 100644
--- a/arch/um/include/shared/sysdep-i386/tls.h
+++ b/arch/um/include/shared/sysdep-i386/tls.h
@@ -21,7 +21,7 @@
 
 # else /* __KERNEL__ */
 
-#  include <asm/ldt.h>
+#  include <ldt.h>
 typedef struct user_desc user_desc_t;
 
 # endif /* __KERNEL__ */