ixgbe: Add a RETA query command to VF-PF channel API

Add this new command for 82599 and x540 devices only. Support for other
devices will be added later.

82599 and x540 VFs and PF share the same RSS redirection table (RETA).
Therefore we just return it for all VFs.

For 82599 and x540 RETA table is an array of 32 registers (128 bytes) and
the maximum number of registers that may be delivered in a single VF-PF
channel command is 15. On the other hand VFs of these devices can be
configured to have up to 4 RSS queues. Therefore we will "compress" the
RETA by transferring only 2 bits per entry and thereby it will take only 8
registers (DWORDS) to transfer the whole VF RETA.

Thus this patch does the following:

  - Adds a new API version (to specify a new commands set).
  - Adds the IXGBE_VF_GET_RETA command to the VF-PF commands set.

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>