i40e: Support for NPAR iSCSI partition with DCB

Add parsing and reporting of iSCSI capability for a given device or
function.

Also add support for iSCSI partition type with DCB in NPAR mode.
In this mode it is expected that software would configure both the LAN
and iSCSI traffic classes for the iSCSI partition; whereas all the NIC
type partitions will use LAN TC (TC0) only.
Hence, the patch enables querying of DCB configuration in MFP mode and
configures TCs for iSCSI partition type.

Though NIC type partitions may not have more than 1 TC enabled for them
the port may have multiple TCs enabled and hence I40E_FLAG_DCB_ENABLED
will be set/reset on all the partitions based on number of TCs on the
port. This is required as in DCB environment it is expected that all
traffic will be priority tagged.

Change-ID: I8c6e1cfd46c46d8a39c57d9020d9ff8d42ed8a7d
Signed-off-by: Neerav Parikh <neerav.parikh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>