net/smc: set ini->smcrv2.ib_dev_v2 to NULL if SMC-Rv2 is unavailable

In the process of checking whether RDMAv2 is available, the current
implementation first sets ini->smcrv2.ib_dev_v2, and then allocates
smc buf desc and register rmb, but the latter may fail. In this case,
the pointer should be reset.

Fixes: e49300a ("net/smc: add listen processing for SMC-Rv2")
Signed-off-by: liuyacan <liuyacan@corp.netease.com>
Reviewed-by: Karsten Graul <kgraul@linux.ibm.com>
Link: https://lore.kernel.org/r/20220525085408.812273-1-liuyacan@corp.netease.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/smc/af_smc.c

@@ -2161,6 +2161,7 @@ static void smc_find_rdma_v2_device_serv(struct smc_sock *new_smc,
 
 not_found:
 	ini->smcr_version &= ~SMC_V2;
+	ini->smcrv2.ib_dev_v2 = NULL;
 	ini->check_smcrv2 = false;
 }