of/device: Replace struct of_device with struct platform_device

of_device is just an alias for platform_device, so remove it entirely.  Also
replace to_of_device() with to_platform_device() and update comment blocks.

This patch was initially generated from the following semantic patch, and then
edited by hand to pick up the bits that coccinelle didn't catch.

@@
@@
-struct of_device
+struct platform_device

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Reviewed-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/fs_enet/mac-fec.c b/drivers/net/fs_enet/mac-fec.c
index 7ca1642..61035fc 100644
--- a/drivers/net/fs_enet/mac-fec.c
+++ b/drivers/net/fs_enet/mac-fec.c
@@ -96,7 +96,7 @@
 
 static int do_pd_setup(struct fs_enet_private *fep)
 {
-	struct of_device *ofdev = to_of_device(fep->dev);
+	struct platform_device *ofdev = to_platform_device(fep->dev);
 
 	fep->interrupt = of_irq_to_resource(ofdev->dev.of_node, 0, NULL);
 	if (fep->interrupt == NO_IRQ)