bpf: Change code to help coccicheck analyze tail calls
bpf: Change code to help coccicheck analyze tail calls

Without these changes, and because Coccinelle doesn't analyze the values
of variables to prune branches, the new Coccinelle script detects the
two tail calls as missing a subsequent DROP_MISSED_TAIL_CALL.

Signed-off-by: Paul Chaignon <a027184a55211cd23e3f3094f1fdc728df5e0500@cilium.io>

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