net/sfc: restart RxQ in case of exception on event queue

net/sfc: restart RxQ in case of exception on event queue

Examples of recoverable exceptions are:
 - unexpected Rx event (Rx scatter abort with non-zero size,
   too big Rx descriptors batch completed)
 - Rx error due to invalid Rx descriptors push
 - Rx error due to Rx descriptor read error (e.g. unmapped Rx ring
   and denied by IOMMU)

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Andrew Lee <alee@solarflare.com>
Reviewed-by: Robert Stonehouse <rstonehouse@solarflare.com>