arm64: include asm/cacheflush.h in asm/hugetlb.h

PG_dcache_clean is used in asm/hugetlb.h but defined in asm/cacheflush.h:
builds rely on an accident of that being included via linux/mempolicy.h,
but better include it directly (like arch/sh/include/asm/hugetlb.h does).

Link: https://lkml.kernel.org/r/bd77cc1b-e83b-f276-9e27-c19e7c9119aa@google.comSigned-off-by: Hugh Dickins <hughd@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/arm64/include/asm/hugetlb.h

@@ -10,6 +10,7 @@
 #ifndef __ASM_HUGETLB_H
 #define __ASM_HUGETLB_H
 
+#include <asm/cacheflush.h>
 #include <asm/page.h>
 
 #ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION