net: team: rename team to team_core for linking

net: team: rename team to team_core for linking

Similar with commit 08d323234d10 ("net: fou: rename the source for linking"),
We'll need to link two objects together to form the team module.
This means the source can't be called team, the build system expects
team.o to be the combined object.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20240401031004.1159713-3-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>