mm: Move pgtable_cache_init() earlier

Some architectures need to initialize SLAB caches to be able
to allocate page tables. They do that from pgtable_cache_init()
so the later should be called earlier now, best is before
vmalloc_init().
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

init/main.c

@@ -547,6 +547,7 @@ static void __init mm_init(void)
 	page_cgroup_init_flatmem();
 	mem_init();
 	kmem_cache_init();
+	pgtable_cache_init();
 	vmalloc_init();
 }
 
@@ -684,7 +685,6 @@ asmlinkage void __init start_kernel(void)
 		late_time_init();
 	calibrate_delay();
 	pidmap_init();
-	pgtable_cache_init();
 	anon_vma_init();
 #ifdef CONFIG_X86
 	if (efi_enabled)