RDMA/hns: Use mutex instead of spinlock for ida allocation

GFP_KERNEL may cause ida_alloc_range() to sleep, but the spinlock covering
this function is not allowed to sleep, so the spinlock needs to be changed
to mutex.

As there is a certain chance of memory allocation failure, GFP_ATOMIC is
not suitable for QP allocation scenarios.

Fixes: 71586dd2

 ("RDMA/hns: Create QP with selected QPN for bank load balance")
Link: https://lore.kernel.org/r/1611048513-28663-1-git-send-email-liweihang@huawei.com
Signed-off-by: Yangyang Li <liyangyang20@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>