[IA64] VIRTUAL_MEM_MAP can be set when DISCONTIGMEM isn't; handle it

Patch developed by Ian Wienand under advice from Bill Irwin.
Signed-off-by: William Irwin <wli@holomorphy.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

include/asm-ia64/page.h

@@ -84,6 +84,13 @@ extern int ia64_pfn_valid (unsigned long pfn);
 #endif
 
 #ifndef CONFIG_DISCONTIGMEM
+# ifdef CONFIG_VIRTUAL_MEM_MAP
+extern struct page *vmem_map;
+#  define pfn_valid(pfn)       (((pfn) < max_mapnr) && ia64_pfn_valid(pfn))
+#  define page_to_pfn(page)    ((unsigned long) (page - vmem_map))
+#  define pfn_to_page(pfn)     (vmem_map + (pfn))
+# endif
+#else /* !CONFIG_VIRTUAL_MEM_MAP */
 #define pfn_valid(pfn)		(((pfn) < max_mapnr) && ia64_pfn_valid(pfn))
 #define page_to_pfn(page)	((unsigned long) (page - mem_map))
 #define pfn_to_page(pfn)	(mem_map + (pfn))