initramfs: clean up messages related to initramfs unpacking

With the removal of duplicate unpack_to_rootfs() (commit
df52092f

) the messages displayed do not
actually correspond to what the kernel is doing.  In addition, depending
if ramdisks are supported or not, the messages are not at all the same.

So keep the messages more in sync with what is really doing the kernel,
and only display a second message in case of failure.  This also ensure
that the printk message cannot be split by other printk's.

Signed-off-by: Eric Piel <eric.piel@tremplin-utc.net>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>