RDMA/core: Convert to use ERR_CAST()

JIRA: https://issues.redhat.com/browse/RHEL-110100

commit 8a94c42
Author: Li Haoran <li.haoran7@zte.com.cn>
Date:   Tue Apr 1 21:10:15 2025 +0800

    RDMA/core: Convert to use ERR_CAST()

    As opposed to open-code, using the ERR_CAST macro clearly indicates that
    this is a pointer to an error value and a type conversion was performed.

    Link: https://patch.msgid.link/r/20250401211015750qxOfU9XZ8QgKizM1Lcyq2@zte.com.cn
    Signed-off-by: Li Haoran <li.haoran7@zte.com.cn>
    Signed-off-by: Shao Mingyin <shao.mingyin@zte.com.cn>
    Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Signed-off-by: Kamal Heib <kheib@redhat.com>

Author: Kamalheib

drivers/infiniband/core/verbs.c

@@ -572,7 +572,7 @@ struct ib_ah *rdma_create_ah(struct ib_pd *pd, struct rdma_ah_attr *ah_attr,
 					   GFP_KERNEL : GFP_ATOMIC);
 	if (IS_ERR(slave)) {
 		rdma_unfill_sgid_attr(ah_attr, old_sgid_attr);
-		return (void *)slave;
+		return ERR_CAST(slave);
 	}
 	ah = _rdma_create_ah(pd, ah_attr, flags, NULL, slave);
 	rdma_lag_put_ah_roce_slave(slave);