arm64: kernel: explicitly add include in armv8_deprecated

Backport requires access to asm/cputype.h, and the implicit
path is not present yet.
diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
index 7922c2e..294db9f 100644
--- a/arch/arm64/kernel/armv8_deprecated.c
+++ b/arch/arm64/kernel/armv8_deprecated.c
@@ -14,6 +14,7 @@

+#include <asm/cputype.h>

Change-Id: I17866130c3e3d5366da888defa586c7ac9875b06