iwlwifi: pcie: fix context info memory leak

If the image loader allocation fails, we leak all the previously
allocated memory. Fix this.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20210115130252.97172cbaa67c.I3473233d0ad01a71aa9400832fb2b9f494d88a11@changeid