i40e: add parsing of flexible filter fields from userdef

Add code to parse the user-def field into a data structure format. This
code is intended to allow future extensions of the user-def field by
keeping all code that actually reads and writes the field into a single
location. This ensures that we do not litter the driver with references
to the user-def field and minimizes the amount of bitwise operations we
need to do on the data.

Add code which parses the lower 32bits into a flexible word and its
offset. This will be used in a future patch to enable flexible filters
which can match on some arbitrary data in the packet payload. For now,
we just return -EOPNOTSUPP when this is used.

Add code to fill in the user-def field when reporting the filter back,
even though we don't actually implement any user-def fields yet.

Additionally, ensure that we mask the extended FLOW_EXT bit from the
flow_type now that we will be accepting filters which have the FLOW_EXT
bit set (and thus make use of the user-def field).

Change-Id: I238845035c179380a347baa8db8223304f5f6dd7
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>