edac: sb_edac: Fix a wrong value setting for the previous value

>From the driver design, the variable limit wants to compare with its
previous value, we should set the value of limit instead of the value
of tmp_mb to the variable prev.

Signed-off-by: Hui Wang <jason77.wang@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/edac/sb_edac.c b/drivers/edac/sb_edac.c
index 843545b..2917887 100644
--- a/drivers/edac/sb_edac.c
+++ b/drivers/edac/sb_edac.c
@@ -763,7 +763,7 @@
 			(u32)TAD_TGT2(reg),
 			(u32)TAD_TGT3(reg),
 			reg);
-		prv = tmp_mb;
+		prv = limit;
 	}
 
 	/*