lib/inflate.c: remove dead code

This is a follow up from a discussion in Xen:

The if-statement tests that `res` is non-zero; meaning the case zero is
never reached.

Link: https://lore.kernel.org/all/7587b503-b2ca-4476-8dc9-e9683d4ca5f0@suse.com/
Link: https://lkml.kernel.org/r/20241219092615.644642-2-ariel.otilibili-anieli@eurecom.fr


Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Ariel Otilibili <ariel.otilibili-anieli@eurecom.fr>
Suggested-by: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Anthony PERARD <anthony.perard@vates.tech>
Cc: Michal Orzel <michal.orzel@amd.com>
Cc: Julien Grall <julien@xen.org>
Cc: Roger Pau Monné <roger.pau@citrix.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>