iwlwifi: pcie: Fix index iteration on free_irq in MSIX mode

In MSIX mode we iterate over the allocated interrupt vectors and
register them to an handler. In case of registration failure,
we free all the allocated irq.
we use the outer index mistakenly instead of the inner one.

Signed-off-by: Haim Dreyfuss <haim.dreyfuss@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>