net: team: Rename enablement functions and struct members to tx

net: team: Rename enablement functions and struct members to tx

Add no functional changes, but rename enablement functions, variables
etc. that are used in teaming driver transmit decisions.

Since rx and tx enablement are still coupled, some of the variables
renamed in this patch are still used for the rx path, but that will
change in a follow-up patch.

Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Marc Harvey <marcharvey@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260409-teaming-driver-internal-v7-6-f47e7589685d@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>