net/smc: code cleanup smc_listen_work

In smc_listen_work() the variables rc and reason_code are defined which
have the same meaning. Eliminate reason_code in favor of the shorter
name rc. No functional changes.
Rename the functions smc_check_ism() and smc_check_rdma() into
smc_find_ism_device() and smc_find_rdma_device() to make there purpose
more clear. No functional changes.

Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>