iwlwifi: mvm: Fix channel switch for count 0 and 1

It was assumed that apply_time==0 implies immediate scheduling, which is
wrong. Instead, the fw expects the START_IMMEDIATELY flag to be set.
Otherwise, this resulted in 0x3063 assert.
Fix that.
While at it rename the T2_V2_START_IMMEDIATELY to
TE_V2_START_IMMEDIATELY.

Fixes: f5d8f50f ("iwlwifi: mvm: Fix channel switch in case of count <= 1")
Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>