NTB: perf: Don't require one more memory window than number of peers

NTB: perf: Don't require one more memory window than number of peers

[ Upstream commit a9c4211ac918ade1522aced6b5acfbe824722f7d ]

ntb_perf should not require more than one memory window per peer. This
was probably an off-by-one error.

Fixes: 5648e56d03fa ("NTB: ntb_perf: Add full multi-port NTB API support")
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Allen Hubbe <allenbh@gmail.com>
Tested-by: Alexander Fomichev <fomichev.ru@gmail.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Sasha Levin <sashal@kernel.org>