IB/{core,hw}: Have ib_umem_get extract the ib_ucontext from ib_udata

ib_umem_get() can only be called in a method callback, which always has a
udata parameter. This allows ib_umem_get() to derive the ucontext pointer
directly from the udata without requiring the drivers to find it in some
way or another.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Shamir Rabinovitch <shamir.rabinovitch@oracle.com>

include/rdma/ib_verbs.h

@@ -4200,6 +4200,7 @@ void rdma_roce_rescan_device(struct ib_device *ibdev);
 
 struct ib_ucontext *ib_uverbs_get_ucontext_file(struct ib_uverbs_file *ufile);
 
+struct ib_ucontext *rdma_get_ucontext(struct ib_udata *udata);
 
 int uverbs_destroy_def_handler(struct uverbs_attr_bundle *attrs);