arm64: kernel: Include _AC definition in page.h

page.h uses '_AC' in the definition of PAGE_SIZE, but doesn't include
linux/const.h where this is defined. This produces build warnings when only
asm/page.h is included by asm code.
Signed-off-by: NJames Morse <james.morse@arm.com>
Acked-by: NMark Rutland <mark.rutland@arm.com>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

arch/arm64/include/asm/page.h

@@ -19,6 +19,8 @@
 #ifndef __ASM_PAGE_H
 #define __ASM_PAGE_H
 
+#include <linux/const.h>
+
 /* PAGE_SHIFT determines the page size */
 /* CONT_SHIFT determines the number of pages which can be tracked together  */
 #ifdef CONFIG_ARM64_64K_PAGES