iwlwifi: mvm: BT Coex - fix copy paste issue

Putting the context id of the primary phy context in
the placeholder of the secondary is obviously a bad
idea.
Spotted by smatch.

Fixes: dac94da8 ("iwlwifi: mvm: new BT Coex API")
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>