iwlwifi: pcie: gen2: fix locking when "HW not ready"

If we run into this error path, we shouldn't unlock the mutex
since it's not locked since. Fix this in the gen2 code as well.

Fixes: eda50cde

 ("iwlwifi: pcie: add context information support")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/iwlwifi.20220128142706.b8b0dfce16ef.Ie20f0f7b23e5911350a2766524300d2915e7b677@changeid