i40e: Fix incorrect use of tx_itr_setting when checking for Rx ITR setup

It looks like there was either a copy/paste error or just a typo that
resulted in the Tx ITR setting being used to determine if we were using
adaptive Rx interrupt moderation or not.

This patch fixes the typo.

Fixes: 65e87c03

 ("i40evf: support queue-specific settings for interrupt moderation")
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>