mm/page_alloc.c: mark bad_range() and meminit_pfn_in_nid() as __maybe_unused

The functions are not used in some configurations.  Adding the attribute
fixes the following warnings when building with clang:

  mm/page_alloc.c:409:19: error: function 'bad_range' is not needed and
      will not be emitted [-Werror,-Wunneeded-internal-declaration]

  mm/page_alloc.c:1106:30: error: unused function 'meminit_pfn_in_nid'
      [-Werror,-Wunused-function]

Link: http://lkml.kernel.org/r/20170518182030.165633-1-mka@chromium.org
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -511,7 +511,7 @@ static int page_is_consistent(struct zone *zone, struct page *page)
 /*
  * Temporary debugging check for pages not lying within a given zone.
  */
-static int bad_range(struct zone *zone, struct page *page)
+static int __maybe_unused bad_range(struct zone *zone, struct page *page)
 {
 	if (page_outside_zone_boundaries(zone, page))
 		return 1;
@@ -521,7 +521,7 @@ static int bad_range(struct zone *zone, struct page *page)
 	return 0;
 }
 #else
-static inline int bad_range(struct zone *zone, struct page *page)
+static inline int __maybe_unused bad_range(struct zone *zone, struct page *page)
 {
 	return 0;
 }
@@ -1297,8 +1297,9 @@ int __meminit early_pfn_to_nid(unsigned long pfn)
 #endif
 
 #ifdef CONFIG_NODES_SPAN_OTHER_NODES
-static inline bool __meminit meminit_pfn_in_nid(unsigned long pfn, int node,
-					struct mminit_pfnnid_cache *state)
+static inline bool __meminit __maybe_unused
+meminit_pfn_in_nid(unsigned long pfn, int node,
+		   struct mminit_pfnnid_cache *state)
 {
 	int nid;
 
@@ -1320,8 +1321,9 @@ static inline bool __meminit early_pfn_in_nid(unsigned long pfn, int node)
 {
 	return true;
 }
-static inline bool __meminit meminit_pfn_in_nid(unsigned long pfn, int node,
-					struct mminit_pfnnid_cache *state)
+static inline bool __meminit  __maybe_unused
+meminit_pfn_in_nid(unsigned long pfn, int node,
+		   struct mminit_pfnnid_cache *state)
 {
 	return true;
 }