uml: tidy pgtable.h

Large pieces of include/asm/pgtable.h were unused cruft.

This uncovered arch/um/kernel/trap.c needing skas.h in order to get
ptrace_faultinfo.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/um/kernel/trap.c

@@ -13,6 +13,7 @@
 #include "as-layout.h"
 #include "kern_util.h"
 #include "os.h"
+#include "skas.h"
 #include "sysdep/sigcontext.h"
 
 /*