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/ibm_newemac/mal.h b/drivers/net/ibm_newemac/mal.h
index 9ededfb..6608421 100644
--- a/drivers/net/ibm_newemac/mal.h
+++ b/drivers/net/ibm_newemac/mal.h
@@ -210,7 +210,7 @@
 	dma_addr_t		bd_dma;
 	struct mal_descriptor	*bd_virt;
 
-	struct of_device	*ofdev;
+	struct platform_device	*ofdev;
 	int			index;
 	spinlock_t		lock;