iwlwifi: mvm: fix a memory leak in iwl_mvm_mac_ctxt_beacon_changed

iwlwifi: mvm: fix a memory leak in iwl_mvm_mac_ctxt_beacon_changed

[ Upstream commit 0f5d44ac6e55551798dd3da0ff847c8df5990822 ]

If beacon_inject_active is true, we will return without freeing
beacon.  Fid that by freeing it before returning.

Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
[reworded the commit message]
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210802172232.d16206ca60fc.I9984a9b442c84814c307cee3213044e24d26f38a@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>