net: constify some inline functions in sock.h

Despite these inline functions having full visibility to the compiler
at compile time, they still strip const from passed pointers.
This change allows for functions in various network drivers to be marked as
const that could not be marked const before.
Signed-off-by: Peter Lafreniere <pjlafren@mtu.edu>
Link: https://lore.kernel.org/r/20220606113458.35953-1-pjlafren@mtu.eduSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/sock.h

@@ -611,7 +611,7 @@ void sock_net_set(struct sock *sk, struct net *net)
 
 int sk_set_peek_off(struct sock *sk, int val);
 
-static inline int sk_peek_offset(struct sock *sk, int flags)
+static inline int sk_peek_offset(const struct sock *sk, int flags)
 {
 	if (unlikely(flags & MSG_PEEK)) {
 		return READ_ONCE(sk->sk_peek_off);
@@ -863,7 +863,7 @@ static inline void sk_add_bind2_node(struct sock *sk, struct hlist_head *list)
 		({ tpos = (typeof(*tpos) *)((void *)pos - offset); 1;});       \
 	     pos = rcu_dereference(hlist_next_rcu(pos)))
 
-static inline struct user_namespace *sk_user_ns(struct sock *sk)
+static inline struct user_namespace *sk_user_ns(const struct sock *sk)
 {
 	/* Careful only use this in a context where these parameters
 	 * can not change and must all be valid, such as recvmsg from
@@ -909,7 +909,7 @@ enum sock_flags {
 
 #define SK_FLAGS_TIMESTAMP ((1UL << SOCK_TIMESTAMP) | (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE))
 
-static inline void sock_copy_flags(struct sock *nsk, struct sock *osk)
+static inline void sock_copy_flags(struct sock *nsk, const struct sock *osk)
 {
 	nsk->sk_flags = osk->sk_flags;
 }