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>

drivers/char/rtc.c

@@ -961,7 +961,7 @@ static int __init rtc_init(void)
 #endif
 #ifdef CONFIG_SPARC32
 	struct device_node *ebus_dp;
-	struct of_device *op;
+	struct platform_device *op;
 #else
 	void *r;
 #ifdef RTC_IRQ