[PATCH] uml: correct error messages in COW driver

Improve some error messages in the COW driver, and say V3, not V2, when
talking about V3 format.  Also resync with our userspace code utility a bit
more.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Acked-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>