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/sunbmac.h b/drivers/net/sunbmac.h
index 8840bc0..8db8894 100644
--- a/drivers/net/sunbmac.h
+++ b/drivers/net/sunbmac.h
@@ -329,8 +329,8 @@
 	unsigned int		timer_ticks;
 
 	struct net_device_stats	enet_stats;
-	struct of_device	*qec_op;
-	struct of_device	*bigmac_op;
+	struct platform_device	*qec_op;
+	struct platform_device	*bigmac_op;
 	struct net_device	*dev;
 };