i40e: keep allocated memory in structs

Save both a pointer to memory and the length in order to store all
info about allocated kernel memory.  This patch changes some adminq
allocations to preserve the full i40e_dma_mem/i40e_virt_mem structs
for every allocation.

Change-Id: Ibcf96159aba4ba61f839d16d87d19478df28e630
Signed-off-by: David Cassard <david.g.cassard@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>