lib/test_hmm: remove set but unused page variable

The HMM selftests use atomic_check_access() to check atomic access to a
page has been revoked.  It doesn't matter if the page mapping has been
removed from the mirrored page tables as that also implies atomic access
has been revoked.  Therefore remove the unused page variable to fix this
compiler warning:

  lib/test_hmm.c:631:16: warning: variable `page' set but not used [-Wunused-but-set-variable]

Link: https://lkml.kernel.org/r/[email protected]
Fixes: b659bae ("mm: selftests for exclusive device memory")
Signed-off-by: Alistair Popple <[email protected]>
Reported-by: Hulk Robot <[email protected]>
Reported-by: kernel test robot <[email protected]>
Reported-by: Yang Yingliang <[email protected]>
Acked-by: Souptick Joarder <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: apopple-nvidia

lib/test_hmm.c

@@ -628,10 +628,8 @@ static int dmirror_check_atomic(struct dmirror *dmirror, unsigned long start,
 
 	for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
 		void *entry;
-		struct page *page;
 
 		entry = xa_load(&dmirror->pt, pfn);
-		page = xa_untag_pointer(entry);
 		if (xa_pointer_tag(entry) == DPT_XA_TAG_ATOMIC)
 			return -EPERM;
 	}