An upcoming change will invoke ath12k_mac_init_arvif(),
ath12k_mac_assign_link_vif(), and ath12k_mac_unassign_link_vif() from a
line located above their current definition. Hence, relocate these
functions to above so that these can be invoked later on.
No functionality changes. Compile tested only.
Signed-off-by: Aditya Kumar Singh <aditya.kumar.singh@xxxxxxxxxxxxxxxx>