lib/c/criu.h: rm explicit numbering of enum elements

C standard specifies that the first enum element is 0 and the next ones
are +1 to a previous element (C90, "3.5.2.2 Enumeration
specifiers").
Therefore, there is no need to explicitly specify element values.

The explicit initializers were added in the first commit introducing
this enum (commit 46e8aeed).

While at it, let's also add a comma after the last element, for any
future patch adding more elements to look better.

No functional change.

Cc: Ruslan Kuprieiev <rkuprieiev@cloudlinux.com>
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Acked-by: Ruslan Kuprieiev <rkuprieiev@cloudlinux.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>