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>
diff --git a/net/Kconfig b/net/Kconfig
index e330594..e926884 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -217,7 +217,7 @@
 
 config RPS
 	boolean
-	depends on SMP && SYSFS
+	depends on SMP && SYSFS && USE_GENERIC_SMP_HELPERS
 	default y
 
 menu "Network testing"