neighbour: Remove unused inline function neigh_key_eq16()

All uses of neigh_key_eq16() have
been removed since commit 1202cdd6 ("Remove DECnet support
from kernel"), so remove it.
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/neighbour.h

@@ -276,11 +276,6 @@ static inline void *neighbour_priv(const struct neighbour *n)
 
 extern const struct nla_policy nda_policy[];
 
-static inline bool neigh_key_eq16(const struct neighbour *n, const void *pkey)
-{
-	return *(const u16 *)n->primary_key == *(const u16 *)pkey;
-}
-
 static inline bool neigh_key_eq32(const struct neighbour *n, const void *pkey)
 {
 	return *(const u32 *)n->primary_key == *(const u32 *)pkey;