net/sfc: support per-queue Rx prefix for EF100

net/sfc: support per-queue Rx prefix for EF100

Riverhead FW supports Rx prefix choice based on required fields in Rx
prefix. The feature is generalized in libefx to provide Rx prefixes
layout for other NICs and firmware variants. Now driver can get
the prefix layout after Rx queue start and use the layout details to
check its expectations or simply in run-time.

Rx prefix choice and query interface is defined in SF-119689-TC
EF100 host interface.

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Andy Moreton <amoreton@xilinx.com>