vmalloc: use kzalloc() instead of alloc_bootmem()

We can call vmalloc_init() after kmem_cache_init() and use kzalloc() instead of
the bootmem allocator when initializing vmalloc data structures.

Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Nick Piggin <npiggin@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

init/main.c

@@ -587,7 +587,6 @@ asmlinkage void __init start_kernel(void)
 	 * kmem_cache_init()
 	 */
 	pidhash_init();
-	vmalloc_init();
 	vfs_caches_init_early();
 	sort_main_extable();
 	trap_init();
@@ -596,6 +595,7 @@ asmlinkage void __init start_kernel(void)
 	 */
 	mem_init();
 	kmem_cache_init();
+	vmalloc_init();
 	/*
 	 * Set up the scheduler prior starting any interrupts (such as the
 	 * timer interrupt). Full topology setup happens at smp_init()