[netdrvr] smc91x: fix resource removal (null ptr deref)

Properly handle resource cleanup on unplug/exit.

Spotted by Jonathan Cameron

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/net/smc91x.c b/drivers/net/smc91x.c
index 2040965..24768c1 100644
--- a/drivers/net/smc91x.c
+++ b/drivers/net/smc91x.c
@@ -2255,7 +2255,7 @@
 
 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "smc91x-regs");
 	if (!res)
-		platform_get_resource(pdev, IORESOURCE_MEM, 0);
+		res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	release_mem_region(res->start, SMC_IO_EXTENT);
 
 	free_netdev(ndev);