Stop assuming the IPA packet status has a fixed format (defined by
a C structure).  Instead, use a function to extract each field from
a block of data interpreted as an IPA packet status.  Define an
enumerated type that identifies the fields that can be extracted.
The current function extracts fields based on the existing
ipa_status structure format (which is no longer used).

Define IPA_STATUS_RULE_MISS, to replace the calls to field_max() to
represent that condition; those depended on the knowing the width of
a filter or router rule in the IPA packet status structure.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>