net/smc: no peer ID in CLC decline for SMCD

Just SMCR requires a CLC Peer ID, but not SMCD. The field should be
zero for SMCD.

Fixes: c758dfdd ("net/smc: add SMC-D support in CLC messages")
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>