iwlwifi: mvm: clarify time event end handling

The code here is a little confusing, the iwl_mvm_te_check_disconnect()
will check that the interface is a station, but going into it after
already having processed the time even end for P2P seems strange at
first look.

Put a switch statement there to distinguish the interface types and
make this more readable.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>