[isa] Fix a small typo in isa.c.

With this patch ISA drivers actually get probed so they have a fair
chance of working now.

Signed-off-by: Pantelis Koukousoulas <pktoss@gmail.com>

src/drivers/bus/isa.c

 	  (driver)->probe_addrs[(ioidx)] )
 
 static struct isa_driver isa_drivers[0]
-	__table_start ( struct isa_driver, isa_driver );
+	__table_start ( struct isa_driver, isa_drivers );
 static struct isa_driver isa_drivers_end[0]
-	__table_end ( struct isa_driver, isa_driver );
+	__table_end ( struct isa_driver, isa_drivers );
 
 static void isabus_remove ( struct root_device *rootdev );