Revert "ksmbd: fix missing RDMA-capable flag for IPoIB device in ksmbd_rdma_capable_netdev()"

This reverts commit ecce70cf.

Revert the GUID trick code causing the layering violation.
I will try to allow the users to turn RDMA-capable on/off via sysfs later

Cc: Kangjing Huang <huangkangjing@gmail.com>
Cc: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>