iavf: fix FDIR rule fields masks validation

Return an error if a field's mask is neither full nor empty. When a mask
is only partial the field is not being used for rule programming but it
gives a wrong impression it is used. Fix by returning an error on any
partial mask to make it clear they are not supported.
The ip_ver assignment is moved earlier in code to allow using it in
iavf_validate_fdir_fltr_masks.

Fixes: 527691bf ("iavf: Support IPv4 Flow Director filters")
Fixes: e90cbc25 ("iavf: Support IPv6 Flow Director filters")
Signed-off-by: Piotr Gardocki <piotrx.gardocki@intel.com>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>