mm/ALPHA: clean up unused VALID_PAGE()

VALID_PAGE() has been removed from kernel long time ago, so clean up it.
Signed-off-by: NJiang Liu <jiang.liu@huawei.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Nadia Yvette Chambers <nyc@holomorphy.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/alpha/include/asm/mmzone.h

@@ -71,8 +71,6 @@ PLAT_NODE_DATA_LOCALNR(unsigned long p, int n)
 
 #define virt_to_page(kaddr)	pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
 
-#define VALID_PAGE(page)	(((page) - mem_map) < max_mapnr)
-
 #define pmd_page(pmd)		(pfn_to_page(pmd_val(pmd) >> 32))
 #define pgd_page(pgd)		(pfn_to_page(pgd_val(pgd) >> 32))
 #define pte_pfn(pte)		(pte_val(pte) >> 32)