scsi: fc: Add mechanism to update FPIN signal statistics

Under fc_host_statistics add statistics for Congestion Signals that are
delivered to the host as interrupt signals.

Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: James Smart <[e-mail]>
Reviewed-by: Himanshu Madhani <[e-mail]>
Signed-off-by: Shyam Sundar <[e-mail]>
Signed-off-by: Nilesh Javali <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/scsi_transport_fc.c

···
 fc_host_statistic(fc_xid_busy);
 fc_host_statistic(fc_seq_not_found);
 fc_host_statistic(fc_non_bls_resp);
+fc_host_statistic(cn_sig_warn);
+fc_host_statistic(cn_sig_alarm);
+
 
 #define fc_host_fpin_statistic(name)					\
 static ssize_t fc_host_fpinstat_##name(struct device *cd,		\
···
 	&device_attr_host_fc_xid_busy.attr,
 	&device_attr_host_fc_seq_not_found.attr,
 	&device_attr_host_fc_non_bls_resp.attr,
+	&device_attr_host_cn_sig_warn.attr,
+	&device_attr_host_cn_sig_alarm.attr,
 	&device_attr_host_reset_statistics.attr,
 	&device_attr_host_fpin_dn.attr,
 	&device_attr_host_fpin_dn_unknown.attr,

include/scsi/scsi_transport_fc.h

···
 	u64 fc_seq_not_found;		/* seq is not found for exchange */
 	u64 fc_non_bls_resp;		/* a non BLS response frame with
 					   a sequence responder in new exch */
+	/* Host Congestion Signals */
+	u64 cn_sig_warn;
+	u64 cn_sig_alarm;
 };