[PATCH] fix build error with CONFIG_BLK_DEV_INITRD=n

[Nicolas Pitre]

populate_rootfs_domain is defined in init/initramfs.c which gets
compiled only if CONFIG_BLK_DEV_INITRD=y.

Signed-off-by: Nicolas Pitre <nicolas.pitre at linaro.org>
---

Would be a good idea to fold in the patch from commit 1b40343e, or 
better yet, find a cleaner solution.

diff --git a/init/main.c b/init/main.c
index 3fe1a78..fbe7a22 100644
--- a/init/main.c
+++ b/init/main.c
@@ -926,11 +926,13 @@ static int __init kernel_init(void * unused)
 
 	(void) sys_dup(0);
 	(void) sys_dup(0);
+#ifdef CONFIG_BLK_DEV_INITRD
 	/*
 	 * We need to ensure that the filesystem is ready by this point, wait for
 	 * async_populate_rootfs to complete.
 	 */
 	async_synchronize_full_domain(&populate_rootfs_domain);
+#endif
 
 	/*
 	 * check if there is an early userspace init.  If yes, let it do all