[PATCH] unify pfn_to_page: ia64 pfn_to_page

ia64 has special config CONFIG_VIRTUAL_MEM_MAP.
CONFIG_DISCONTIGMEM=y && CONFIG_VIRTUAL_MEM_MAP!=y is bug ?

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>