net/smc: check for ip prefix and subnet

net/smc: check for ip prefix and subnet

The check for a matching ip prefix and subnet was only done for SMC-R
in smc_listen_rdma_check() but not when an SMC-D connection was
possible. Rename the function into smc_listen_prfx_check() and move its
call to a place where it is called for both SMC variants.
And add a new CLC DECLINE reason for the case when the IP prefix or
subnet check fails so the reason for the failing SMC connection can be
found out more easily.

Signed-off-by: Karsten Graul <[email protected]>
Signed-off-by: Ursula Braun <[email protected]>
Signed-off-by: David S. Miller <[email protected]>