net: RPS needs to depend upon USE_GENERIC_SMP_HELPERS

You cannot invoke __smp_call_function_single() unless the
architecture sets this symbol.
Reported-by: Daniel Hellstrom <daniel@gaisler.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/Kconfig

@@ -217,7 +217,7 @@ source "net/dns_resolver/Kconfig"
 
 config RPS
 	boolean
-	depends on SMP && SYSFS
+	depends on SMP && SYSFS && USE_GENERIC_SMP_HELPERS
 	default y
 
 menu "Network testing"