ksmbd: detect RDMA capable netdevs include IPoIB

ksmbd: detect RDMA capable netdevs include IPoIB

Current ksmbd_rdma_capable_netdev fails to mark certain RDMA-capable
inerfaces such as IPoIB as RDMA capable after reverting GUID matching code
due to layer violation.
This patch check the ARPHRD_INFINIBAND type safely identifies an IPoIB
interface without introducing a layer violation, ensuring RDMA
functionality is correctly enabled for these interfaces.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>