sfc: make function efx_rps_hash_bucket static

The function efx_rps_hash_bucket is local to the source and
does not need to be in global scope, so make it static.

Cleans up sparse warning:
symbol 'efx_rps_hash_bucket' was not declared. Should it be static?
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/efx.c

@@ -3180,6 +3180,7 @@ bool efx_rps_check_rule(struct efx_arfs_rule *rule, unsigned int filter_idx,
 	return true;
 }
 
+static
 struct hlist_head *efx_rps_hash_bucket(struct efx_nic *efx,
 				       const struct efx_filter_spec *spec)
 {