mmc: sdhci-s3c: fix potential NULL dereference

sc->clk_bus[ptr] could be NULL.

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/drivers/mmc/host/sdhci-s3c.c b/drivers/mmc/host/sdhci-s3c.c
index 82709b6..3d00e72 100644
--- a/drivers/mmc/host/sdhci-s3c.c
+++ b/drivers/mmc/host/sdhci-s3c.c
@@ -567,8 +567,10 @@
 
  err_req_regs:
 	for (ptr = 0; ptr < MAX_BUS_CLK; ptr++) {
-		clk_disable(sc->clk_bus[ptr]);
-		clk_put(sc->clk_bus[ptr]);
+		if (sc->clk_bus[ptr]) {
+			clk_disable(sc->clk_bus[ptr]);
+			clk_put(sc->clk_bus[ptr]);
+		}
 	}
 
  err_no_busclks: