um: mmu: remove stub_pages

I removed all the users of this some time ago, but
evidently forgot the pointers. Remove them from the
data structure too.

Fixes: bfc58e2b98 ("um: remove process stub VMA")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/include/asm/mmu.h

@@ -12,7 +12,6 @@
 typedef struct mm_context {
 	struct mm_id id;
 	struct uml_arch_mm_context arch;
-	struct page *stub_pages[2];
 } mm_context_t;
 
 extern void __switch_mm(struct mm_id * mm_idp);