common/sfc_efx/base: add API to compare match specs

common/sfc_efx/base: add API to compare match specs

Match specification format and its size are not exposed to clients.
Provide an API to compare two match specifications.

A client would typically use this API to compare a match specification
of an outer rule being validated with match specifications of already
active outer rules (to make sure that rule class is supported).

Signed-off-by: Ivan Malov <ivan.malov@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Andy Moreton <amoreton@xilinx.com>