netdev-tc-offloads: Fix incorrect mask in probe_multi_mask_per_prio().

netdev-tc-offloads: Fix incorrect mask in probe_multi_mask_per_prio().

Presumably this was meant to be all-one-bits but it wasn't.  It also didn't
have the right endianness for an ovs_be16, so "sparse" complained.

CC: Paul Blakey <paulb@mellanox.com>
CC: Simon Horman <simon.horman@netronome.com>
Fixes: d00eeded6a9b ("netdev-tc-offloads: Probe for allowing multiple masks on single priority")
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Justin Pettit <jpettit@ovn.org>