Makefile: Fix duplicates in cscope output
Makefile: Fix duplicates in cscope output

For some reason, some files would show up multiple times in the
GOLANG_SRCFILES variable, which would cause cscope to create duplicate
references to symbols across the codebase. Pass the list through sort
and uniq to ensure each file is only scanned once.

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

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