mtd: mxc_nand: fix unbalanced clk_disable() in error path

If nand_scan_ident() or nand_scan_tail() fails, the NAND chip may have
been deselected and the clock already disabled. Thus, check 'clk_act'
in the error path to decide whether the clock still needs to be
disabled.

This fixes a:
|WARNING: at drivers/clk/clk.c:472 __clk_disable+0x3c/0x78()
Signed-off-by: NLothar Waßmann <LW@KARO-electronics.de>
Acked-by: NSascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NArtem Bityutskiy <artem.bityutskiy@linux.intel.com>

drivers/mtd/nand/mxc_nand.c

@@ -1533,7 +1533,8 @@ static int mxcnd_probe(struct platform_device *pdev)
 	return 0;
 
 escan:
-	clk_disable_unprepare(host->clk);
+	if (host->clk_act)
+		clk_disable_unprepare(host->clk);
 
 	return err;
 }