uml: SMP locking commentary

Add some more commentary about various pieces of global data not needing
locking.

Also got rid of unmap_physmem since that is no longer used.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c
index 3c6c44c..ca71577 100644
--- a/arch/um/drivers/net_kern.c
+++ b/arch/um/drivers/net_kern.c
@@ -368,7 +368,6 @@
 		.name  = DRIVER_NAME,
 	},
 };
-static int driver_registered;
 
 static void net_device_release(struct device *dev)
 {
@@ -383,6 +382,12 @@
 	free_netdev(netdev);
 }
 
+/*
+ * Ensures that platform_driver_register is called only once by
+ * eth_configure.  Will be set in an initcall.
+ */
+static int driver_registered;
+
 static void eth_configure(int n, void *init, char *mac,
 			  struct transport *transport)
 {