RDMA/rtrs-srv: Fix modinfo output for stringify

RDMA/rtrs-srv: Fix modinfo output for stringify

BugLink: https://bugs.launchpad.net/bugs/1990162
[ Upstream commit ed6e53820ee4f68ed927de17e5675ff2a07a47e2 ]

stringify works with define, not enum.

Fixes: 91fddedd439c ("RDMA/rtrs: private headers with rtrs protocol structs and helpers")
Cc: jinpu.wang@ionos.com
Link: https://lore.kernel.org/r/20220712103113.617754-2-haris.iqbal@ionos.com
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Md Haris Iqbal <haris.iqbal@ionos.com>
Reviewed-by: Aleksei Marov <aleksei.marov@ionos.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>