hwrng: via-rng - Mark device ID table as __maybe_unused

It is only used in modular builds.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/via-rng.c

@@ -221,7 +221,7 @@ static void __exit mod_exit(void)
 module_init(mod_init);
 module_exit(mod_exit);
 
-static struct x86_cpu_id via_rng_cpu_id[] = {
+static struct x86_cpu_id __maybe_unused via_rng_cpu_id[] = {
 	X86_FEATURE_MATCH(X86_FEATURE_XSTORE),
 	{}
 };