iwlwifi: pcie: request one more interrupt vector

We want to request an interrupt vector for RSS queue per CPU,
one vector for fallback queue, and one for non-rx interrupts.
Future patch will make sure that no RSS traffic is directed to
fallback queue.
This will enable us to enable fast path on traffic that otherwise
would have been received on the fallback queue.

Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>