ixgbe: Don't assume dev->num_tc is equal to hardware TC config

The code throughout ixgbe was assuming that dev->num_tc was populated and
configured with the driver, when in fact this can be configured via mqprio
without any hardware coordination other than restricting us to the real
number of Tx queues we advertise.

Instead of handling things this way we need to keep a local copy of the
number of TCs in use so that we don't accidentally pull in the TC
configuration from mqprio when it is configured in software mode.

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>