net/sfc: avoid Rx queue setup failure if thresholds are set

net/sfc: avoid Rx queue setup failure if thresholds are set

Rx queue prefetch, host and writeback thresholds are used for
performance fine-tuning and not applicable to Solarflare NICs.
It is safe to just log warning and do not fail Rx queue setup
to be more friendly to DPDK applications which hardcode it.

Fixes: ce35b05c635e ("net/sfc: implement Rx queue setup release operations")
Cc: stable@dpdk.org
Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>