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: NHui Wang <jason77.wang@gmail.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/edac/sb_edac.c

@@ -763,7 +763,7 @@ static void get_memory_layout(const struct mem_ctl_info *mci)
 			(u32)TAD_TGT2(reg),
 			(u32)TAD_TGT3(reg),
 			reg);
-		prv = tmp_mb;
+		prv = limit;
 	}
 
 	/*