arm64: add <asm/asm-prototypes.h>

While we can export symbols from assembly files, CONFIG_MODVERIONS requires C
declarations of anyhting that's exported.

Let's account for this as other architectures do by placing these declarations
in <asm/asm-prototypes.h>, which kbuild will automatically use to generate
modversion information for assembly files.

Since we already define most prototypes in existing headers, we simply need to
include those headers in <asm/asm-prototypes.h>, and don't need to duplicate
these.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/asm-prototypes.h

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_PROTOTYPES_H
+#define __ASM_PROTOTYPES_H
+/*
+ * CONFIG_MODEVERIONS requires a C declaration to generate the appropriate CRC
+ * for each symbol. Since commit:
+ *
+ *   4efca4ed05cbdfd1 ("kbuild: modversions for EXPORT_SYMBOL() for asm")
+ *
+ * ... kbuild will automatically pick these up from <asm/asm-prototypes.h> and
+ * feed this to genksyms when building assembly files.
+ */
+#include <linux/arm-smccc.h>
+
+#include <asm/ftrace.h>
+#include <asm/page.h>
+#include <asm/string.h>
+#include <asm/uaccess.h>
+
+#include <asm-generic/asm-prototypes.h>
+
+long long __ashlti3(long long a, int b);
+long long __ashrti3(long long a, int b);
+long long __lshrti3(long long a, int b);
+
+#endif /* __ASM_PROTOTYPES_H */