drivers/of: fix build error when CONFIG_PPC_DCR is set

Commit 94c09319 (of:
Merge of_device_alloc() and of_device_make_bus_id()) moved code that
does calls a dcr routine without including the correct header which
causes the following build error on some powerpc configurations:

drivers/of/platform.c: In function 'of_device_make_bus_id':
drivers/of/platform.c:437: error: implicit declaration of function 'of_translate_dcr_address'

This patch adds the appropriate header to drivers/of/platform.c
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

drivers/of/platform.c

@@ -19,6 +19,10 @@
 #include <linux/of_device.h>
 #include <linux/of_platform.h>
 
+#if defined(CONFIG_PPC_DCR)
+#include <asm/dcr.h>
+#endif
+
 extern struct device_attribute of_platform_device_attrs[];
 
 static int of_platform_bus_match(struct device *dev, struct device_driver *drv)