arm64: alternatives: make apply_alternatives_vdso() static

We define and use apply_alternatives_vdso() within alternative.c, and
don't provide a prototype in a header. There's no need for it to be
visible outside of alternative.c, so mark it as static.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20221117131650.4056636-1-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/kernel/alternative.c

@@ -196,7 +196,7 @@ static void __apply_alternatives(const struct alt_region *region,
 	}
 }
 
-void apply_alternatives_vdso(void)
+static void apply_alternatives_vdso(void)
 {
 	struct alt_region region;
 	const struct elf64_hdr *hdr;