iccpd - remove unused function

[maipbui]

ADO 27008034

Why I did it

set_route_by_linux_route() is not called by any function within this repo and its submodules, checked on 202106 branch and master branch

git grep --recurse-submodules "set_route_by_linux_route"
src/iccpd/src/mlacp_link_handler.c:static void set_route_by_linux_route(struct CSM* csm,
src/iccpd/src/mlacp_link_handler.c:            /*set_route_by_linux_route(csm, set_l3_local_if, 1);*/   /*add static route by linux route tool*/
src/iccpd/src/mlacp_link_handler.c:            /*set_route_by_linux_route(csm, set_l3_local_if, 0);*/    /*del static route by linux route tool*/

How I did it

Remove unused function set_route_by_linux_route()

How to verify it

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111
• 202205
• 202305

Description for the changelog

A picture of a cute animal (not mandatory but encouraged)

[maipbui]

@gechiang Can we merge this PR? looks like there's no code sync from sonic-net repo.