ipv6: fix _DEVADD() and _DEVUPD() macros

ipv6: fix _DEVADD() and _DEVUPD() macros

ip6_rcv_core() is using:

	__IP6_ADD_STATS(net, idev,
			IPSTATS_MIB_NOECTPKTS +
				(ipv6_get_dsfield(hdr) & INET_ECN_MASK),
			max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));

This is currently evaluating both expressions twice.

Fix _DEVADD() and _DEVUPD() macros to evaluate their arguments once.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250319212516.2385451-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>