cxl/test: Assign overflow_err_count from log->nr_overflow

mock_get_event() uses an uninitialized local variable, nr_overflow, to
populate the overflow_err_count field. That results in incorrect
overflow_err_count values in mocked cxl_overflow trace events, such as
this case where the records are reported as 0 and should be non-zero:

[] cxl_overflow: memdev=mem7 host=cxl_mem.6 serial=7: log=Failure : 0 records from 1763228189130895685 to 1763228193130896180

Fix by using log->nr_overflow and remove the unused local variable.

A follow-up change was considered in cxl_mem_get_records_log() to
confirm that the overflow_err_count is non-zero when the overflow flag
is set [1]. Since the driver has no functional dependency on this
constraint, and a device that violates this specific requirement does
not cause incorrect driver behavior, no validation check is added.

[1] CXL 3.2, Table 8-65 Get Event Records Output Payload

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>> ---
Link: https://patch.msgid.link/20251116013036.1713313-1-alison.schofield@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

Author: AlisonSchofield

tools/testing/cxl/test/mem.c

@@ -256,7 +256,6 @@ static int mock_get_event(struct device *dev, struct cxl_mbox_cmd *cmd)
 {
 	struct cxl_get_event_payload *pl;
 	struct mock_event_log *log;
-	u16 nr_overflow;
 	int ret_limit;
 	u8 log_type;
 	int i;
@@ -299,7 +298,7 @@ static int mock_get_event(struct device *dev, struct cxl_mbox_cmd *cmd)
 		u64 ns;
 
 		pl->flags |= CXL_GET_EVENT_FLAG_OVERFLOW;
-		pl->overflow_err_count = cpu_to_le16(nr_overflow);
+		pl->overflow_err_count = cpu_to_le16(log->nr_overflow);
 		ns = ktime_get_real_ns();
 		ns -= 5000000000; /* 5s ago */
 		pl->first_overflow_timestamp = cpu_to_le64(ns);