ixgbevf: Refactor ring parameter re-size

The function to resize the Tx/Rx rings had the potential to
dereference a NULL pointer and the code would attempt to resize
the Tx ring even if the Rx ring allocation had failed.  This
would cause some confusion in the return code semantics.  Fixed
up to just unwind the allocations if any of them fail and return
an error.

Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Tested-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>