net/smc: fix null pointer dereference in smc_listen_decline()

smc_listen_work() calls smc_listen_decline() on label out_decl,
providing the ini pointer variable. But this pointer can still be null
when the label out_decl is reached.
Fix this by checking the ini variable in smc_listen_work() and call
smc_listen_decline() with the result directly.

Fixes: a7c9c5f4 ("net/smc: CLC accept / confirm V2")
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>