ddr: altera: Repair uninited variable

Fix the following problem:
drivers/ddr/altera/sequencer.c: In function 'sdram_calibration_full':
drivers/ddr/altera/sequencer.c:1943:25: warning: 'found_failing_read' may be used uninitialized in this function [-Wmaybe-uninitialized]
  if (found_passing_read && found_failing_read)
                         ^
drivers/ddr/altera/sequencer.c:1803:26: note: 'found_failing_read' was declared here
  u32 found_passing_read, found_failing_read, initial_failing_dtap;
                          ^

Signed-off-by: Marek Vasut <marex@denx.de>
diff --git a/drivers/ddr/altera/sequencer.c b/drivers/ddr/altera/sequencer.c
index f3621cf..79c265f 100644
--- a/drivers/ddr/altera/sequencer.c
+++ b/drivers/ddr/altera/sequencer.c
@@ -1800,7 +1800,7 @@
 	u32 d, p, i;
 	u32 dtaps_per_ptap;
 	u32 work_bgn, work_end;
-	u32 found_passing_read, found_failing_read, initial_failing_dtap;
+	u32 found_passing_read, found_failing_read = 0, initial_failing_dtap;
 	int ret;
 
 	debug("%s:%d %u\n", __func__, __LINE__, grp);