net/smc: Add SMC-D Linkgroup diagnostic support

mainline inclusion
from mainline-v5.11-rc1
commit 8f9dde4b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I78IFM
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=8f9dde4bf230f5c54a24c42a989dd9d88ec95695



--------------------------------

Deliver SMCD Linkgroup information via netlink based
diagnostic interface.

Signed-off-by: Guvenc Gulce <guvenc@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Yingyu Zeng <zengyingyu@sangfor.com.cn>