x86: ioremap, remove WARN_ON()

Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/mm/ioremap.c

@@ -134,8 +134,6 @@ static void __iomem *__ioremap(unsigned long phys_addr, unsigned long size,
 			return NULL;
 	}
 
-	WARN_ON_ONCE(page_is_ram(pfn));
-
 	switch (mode) {
 	case IOR_MODE_UNCACHED:
 	default: