net: smc911x: avoid unused variable warnings

The change to use the generic DMA engine API in the smc911x
driver has led to a harmless warning about unused local variables:

smsc/smc911x.c: In function 'smc911x_probe':
smsc/smc911x.c:1796:20: error: unused variable 'param'
smsc/smc911x.c:1795:17: error: unused variable 'mask'
smsc/smc911x.c:1794:26: error: unused variable 'config'

This puts the variable declarations inside of the same #ifdef
that protects their use.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 79d3b59a ("net: smc911x: convert pxa dma to dmaengine")
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/smsc/smc911x.c

@@ -1791,9 +1791,11 @@ static int smc911x_probe(struct net_device *dev)
 	unsigned int val, chip_id, revision;
 	const char *version_string;
 	unsigned long irq_flags;
+#ifdef SMC_USE_DMA
 	struct dma_slave_config	config;
 	dma_cap_mask_t mask;
 	struct pxad_param param;
+#endif
 
 	DBG(SMC_DEBUG_FUNC, dev, "--> %s\n", __func__);