NOMMU: is_vmalloc_addr() won't compile if !MMU

Make is_vmalloc_addr() contingent on CONFIG_MMU=y, as it won't compile
in !MMU mode.

[ Bug introduced in commit 9e2779fa:
  "is_vmalloc_addr(): Check if an address is within the vmalloc
  boundaries" ].
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Greg Ungerer <gerg@snapgear.com>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm.h

@@ -235,6 +235,7 @@ static inline int get_page_unless_zero(struct page *page)
 struct page *vmalloc_to_page(const void *addr);
 unsigned long vmalloc_to_pfn(const void *addr);
 
+#ifdef CONFIG_MMU
 /* Determine if an address is within the vmalloc range */
 static inline int is_vmalloc_addr(const void *x)
 {
@@ -242,6 +243,7 @@ static inline int is_vmalloc_addr(const void *x)
 
 	return addr >= VMALLOC_START && addr < VMALLOC_END;
 }
+#endif
 
 static inline struct page *compound_head(struct page *page)
 {