drivers/rtc/rtc-mxc.c: check the return value from clk_prepare_enable()

clk_prepare_enable() may fail, so let's check its return value and
propagate it in the case of error.

Signed-off-by: Fabio Estevam <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/rtc/rtc-mxc.c

···
 		return PTR_ERR(pdata->clk);
 	}
 
-	clk_prepare_enable(pdata->clk);
+	ret = clk_prepare_enable(pdata->clk);
+	if (ret)
+		return ret;
+
 	rate = clk_get_rate(pdata->clk);
 
 	if (rate == 32768)