MIPS: Fix wrong comments in asm/prom.h

In arch/mips/include/asm/prom.h, it should use "!CONFIG_USE_OF"
after #else and #endif.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/include/asm/prom.h

@@ -20,9 +20,9 @@ struct boot_param_header;
 extern void __dt_setup_arch(void *bph);
 extern int __dt_register_buses(const char *bus0, const char *bus1);
 
-#else /* CONFIG_OF */
+#else /* !CONFIG_USE_OF */
 static inline void device_tree_init(void) { }
-#endif /* CONFIG_OF */
+#endif /* !CONFIG_USE_OF */
 
 extern char *mips_get_machine_name(void);
 extern void mips_set_machine_name(const char *name);