ixgbe: move msix_entries allocation into ixgbe_acquire_msix_vectors

We already have to kfree this value if we fail, and this is only part of
MSI-X mode, so we should simply allocate the value where we need it.
This is cleaner, and makes it a lot more obvious why we are freeing it
inside of ixgbe_acquire_msix_vectors.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>