i40e: rework vector reservation

i40e: rework vector reservation

The initial problem solved here is that the vector allocation was trying
too hard to save vectors for VMDq, to the point of not giving the PF enough
when in a tight situation such as an NPAR partition.  This change makes
sure that the PF will get all the queues and vectors it wants to fill
out its destiny.  Essentially, nothing is specially reserved for VMDq,
it simply gets whatever is left after the PF, FCoE, and FD sideband get
what they want.

Additionally, the calculations for the reservations were harder to follow
than necessary, so I've made it more straight forward.

Change-ID: I99b384f104535b686c690b8ef0a787559485c8d4
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>