initrd: mark initrd support as deprecated

The classic initial ramdisk has been replaced by the much more
flexible and efficient initramfs a long time.  Warn about it being
removed soon.

Includes a spelling fix from Colin Ian King <colin.king@canonical.com>.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>

init/do_mounts_initrd.c

@@ -75,6 +75,8 @@ static void __init handle_initrd(void)
 	extern char *envp_init[];
 	int error;
 
+	pr_warn("using deprecated initrd support, will be removed in 2021.\n");
+
 	real_root_dev = new_encode_dev(ROOT_DEV);
 	create_dev("/dev/root.old", Root_RAM0);
 	/* mount initrd on rootfs' /root */