sfc: suppress duplicate nvmem partition types in efx_ef10_mtd_probe
Use a bitmap to keep track of which partition types we've already seen;
for duplicates, return -EEXIST from efx_ef10_mtd_probe_partition() and
thus skip adding that partition.
Duplicate partitions occur because of the A/B backup scheme used by newer
sfc NICs. Prior to this patch they cause sysfs_warn_dup errors because
they have the same name, causing us not to expose any MTDs at all.
Signed-off-by: Edward Cree <ecree@solarflare.com> Signed-off-by: David S. Miller <davem@davemloft.net>