tools/testing/scatterlist: add missing defines

The cited commits replaced preemptible with pagefault_disabled and
flush_kernel_dcache_page with flush_dcache_page respectively, hence need
to update the corresponding defines in the test.

  scatterlist.c: In function ‘sg_miter_stop’:
  scatterlist.c:919:4: warning: implicit declaration of function ‘flush_dcache_page’ [-Wimplicit-function-declaration]
      flush_dcache_page(miter->page);
      ^~~~~~~~~~~~~~~~~
  In file included from linux/scatterlist.h:8:0,
                   from scatterlist.c:9:
  scatterlist.c:922:18: warning: implicit declaration of function ‘pagefault_disabled’ [-Wimplicit-function-declaration]
      WARN_ON_ONCE(!pagefault_disabled());
                    ^
  linux/mm.h:23:25: note: in definition of macro ‘WARN_ON_ONCE’
    int __ret_warn_on = !!(condition);                      \
                           ^~~~~~~~~

Link: https://lkml.kernel.org/r/20220118082105.1737320-1-maorg@nvidia.com
Fixes: 723aca20 ("mm/scatterlist: replace the !preemptible warning in sg_miter_stop()")
Fixes: 0e84f5db ("scatterlist: replace flush_kernel_dcache_page with flush_dcache_page")
Signed-off-by: Maor Gottlieb <maorg@nvidia.com>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/testing/scatterlist/linux/mm.h

@@ -74,7 +74,7 @@ static inline unsigned long page_to_phys(struct page *page)
 	      __UNIQUE_ID(min1_), __UNIQUE_ID(min2_),   \
 	      x, y)
 
-#define preemptible() (1)
+#define pagefault_disabled() (0)
 
 static inline void *kmap(struct page *page)
 {
@@ -127,6 +127,7 @@ kmalloc_array(unsigned int n, unsigned int size, unsigned int flags)
 #define kmemleak_free(a)
 
 #define PageSlab(p) (0)
+#define flush_dcache_page(p)
 
 #define MAX_ERRNO	4095