MIPS: prepare for user enabling of CONFIG_OF

In preparation to allow users to enable DeviceTree without arch or
machine selecting it, we need to fix build errors on MIPS. When
CONFIG_OF is enabled, device_tree_init cannot be resolved. This is
trivially fixed by using CONFIG_USE_OF instead of CONFIG_OF for prom.h.

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/include/asm/prom.h b/arch/mips/include/asm/prom.h
index 8ebc2aa..0b4b668 100644
--- a/arch/mips/include/asm/prom.h
+++ b/arch/mips/include/asm/prom.h
@@ -11,7 +11,7 @@
 #ifndef __ASM_PROM_H
 #define __ASM_PROM_H
 
-#ifdef CONFIG_OF
+#ifdef CONFIG_USE_OF
 #include <linux/bug.h>
 #include <linux/io.h>
 #include <linux/types.h>