RDMA: Handle AH allocations by IB/core

Simplify drivers by ensuring lifetime of ib_ah object. The changes
in .create_ah() go hand in hand with relevant update in .destroy_ah().

We will use this opportunity and convert .destroy_ah() to don't fail, as
it was suggested a long time ago, because there is nothing to do in case
of failure during destroy.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/bnxt_re/main.c

@@ -637,6 +637,7 @@ static const struct ib_device_ops bnxt_re_dev_ops = {
 	.query_srq = bnxt_re_query_srq,
 	.reg_user_mr = bnxt_re_reg_user_mr,
 	.req_notify_cq = bnxt_re_req_notify_cq,
+	INIT_RDMA_OBJ_SIZE(ib_ah, bnxt_re_ah, ib_ah),
 	INIT_RDMA_OBJ_SIZE(ib_pd, bnxt_re_pd, ib_pd),
 	INIT_RDMA_OBJ_SIZE(ib_ucontext, bnxt_re_ucontext, ib_uctx),
 };