memory: of: Remove unused headers

The of_memory.c does not use platform_device nor linked list.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

drivers/memory/of_memory.c

@@ -7,8 +7,6 @@
  */
 
 #include <linux/device.h>
-#include <linux/platform_device.h>
-#include <linux/list.h>
 #include <linux/of.h>
 #include <linux/gfp.h>
 #include <linux/export.h>