bpf: Use CB_PROXY_MAGIC to store proxy meta magic
bpf: Use CB_PROXY_MAGIC to store proxy meta magic

Use the define here to improve readability and locating the code that
changes specific offsets in the context metadata (eg skb->cb). The value
is the same, this is a purely cosmetic change.

Signed-off-by: Joe Stringer <16a9a54ddf4259952e3c118c763138e83693d7fd@cilium.io>

michi-covalent/cilium,tgraf/cilium,michi-covalent/cilium,cilium/cilium,tgraf/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,tklauser/cilium,cilium/cilium,cilium/cilium,tklauser/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,tklauser/cilium,tgraf/cilium,tklauser/cilium,cilium-team/cilium,cilium-team/cilium