ipvs: use explicitly signed chars

ipvs: use explicitly signed chars

[ Upstream commit c1366c7603900d8b55b0baebc0900086e0627435 ]

The `char` type with no explicit sign is sometimes signed and sometimes
unsigned. This code will break on platforms such as arm, where char is
unsigned. So mark it here as explicitly signed, so that the
todrop_counter decrement and subsequent comparison is correct.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>