x86, um: get rid of uml highmem.h

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/asm/fixmap.h b/arch/um/include/asm/fixmap.h
index 9d2be52..69c0252 100644
--- a/arch/um/include/asm/fixmap.h
+++ b/arch/um/include/asm/fixmap.h
@@ -6,6 +6,7 @@
 #include <asm/kmap_types.h>
 #include <asm/archparam.h>
 #include <asm/page.h>
+#include <linux/threads.h>
 
 /*
  * Here we define all the compile-time 'special' virtual