RDMA: Fix kernel-doc warnings about wrong comment

Compilation with W=1 produces warnings similar to the below.

  drivers/infiniband/ulp/ipoib/ipoib_main.c:320: warning: This comment
	starts with '/**', but isn't a kernel-doc comment. Refer
	Documentation/doc-guide/kernel-doc.rst

All such occurrences were found with the following one line
 git grep -A 1 "\/\*\*" drivers/infiniband/

Link: https://lore.kernel.org/r/e57d5f4ddd08b7a19934635b44d6d632841b9ba7.1623823612.git.leonro@nvidia.com
Reviewed-by: Jack Wang <jinpu.wang@ionos.com> #rtrs
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>