wifi: iwlwifi: cleanup EMLSR when BT is active handling

BT Coex disables EMLSR only for a 2.4 GHz link, but doesn't block the
vif from using EMLSR with a different link pair. In addition, storing it
in mvmvif:disable_esr_reason requires extracting the BT Coex bit before
checking if EMLSR is blocked or not for a specific vif.

Therefore, change the BT Coex bit to be an exit reason and not a
blocker. On link selection, EMLSR mode will be re-calculated for the 2.4
GHz link instead of checking that bit.

While at it, move the relevant function declarations to the EMLSR
functions area in mvm.h

Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240505091420.a2e93b67c895.I183a0039ef076613144648cc46fbe9ab3d47c574@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>