microblaze: add missing CONFIG_ prefixes

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Acked-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

arch/microblaze/mm/init.c

@@ -304,11 +304,11 @@ asmlinkage void __init mmu_init(void)
 	/* Map in all of RAM starting at CONFIG_KERNEL_START */
 	mapin_ram();
 
-#ifdef HIGHMEM_START_BOOL
-	ioremap_base = HIGHMEM_START;
+#ifdef CONFIG_HIGHMEM_START_BOOL
+	ioremap_base = CONFIG_HIGHMEM_START;
 #else
 	ioremap_base = 0xfe000000UL;	/* for now, could be 0xfffff000 */
-#endif /* CONFIG_HIGHMEM */
+#endif /* CONFIG_HIGHMEM_START_BOOL */
 	ioremap_bot = ioremap_base;
 
 	/* Initialize the context management stuff */