RDMA/erdma: Fix refcount leak in erdma_mmap

RDMA/erdma: Fix refcount leak in erdma_mmap

[ Upstream commit ee84146c05ad2316b9a7222d0ec4413e0bf30eeb ]

rdma_user_mmap_entry_get() take reference, we should release it when not
need anymore, add the missing rdma_user_mmap_entry_put() in the error
path to fix it.

Fixes: 155055771704 ("RDMA/erdma: Add verbs implementation")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Link: https://lore.kernel.org/r/20221220121139.1540564-1-linmq006@gmail.com
Acked-by: Cheng Xu <chengyou@linux.alibaba.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>