xtensa: ISS: fix command line parameter name

Now 'ethX=...' syntax can actually be used in kernel command line to
specify network interfaces.
Signed-off-by: NMax Filippov <jcmvbkbc@gmail.com>
Signed-off-by: NChris Zankel <chris@zankel.net>

arch/xtensa/platforms/iss/network.c

@@ -681,7 +681,7 @@ static int __init iss_net_setup(char *str)
 
 #undef ERR
 
-__setup("eth=", iss_net_setup);
+__setup("eth", iss_net_setup);
 
 /*
  * Initialize all ISS Ethernet devices previously registered in iss_net_setup.