chore: fix `clang-tidy` warnings

Fix warnings introduced by previous commit.

Change-Id: I3884f8a774860905ddf3d4554f986fde16ec9919
Signed-off-by: Karl Meakin <karl.meakin@arm.com>
diff --git a/inc/hf/arch/std.h b/inc/hf/arch/std.h
index 91f808e..d1c8b7a 100644
--- a/inc/hf/arch/std.h
+++ b/inc/hf/arch/std.h
@@ -13,8 +13,10 @@
 
 #define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
 
+/* NOLINTNEXTLINE(readability-redundant-declaration) */
 int memcmp(const void *a, const void *b, size_t n);
 
+/* NOLINTNEXTLINE(readability-redundant-declaration) */
 int strncmp(const char *a, const char *b, size_t n);
 
 #define ctz(x) __builtin_ctz(x)