extcon: sm5502: Clean up codes by using checkpatch script

extcon: sm5502: Clean up codes by using checkpatch script

This patch just clean up codes by using checkpatch script and fix warning
message about if statement.

- the result of checkpatch script as following:
WARNING: void function return statements are not generally useful
+	return;
+}

WARNING: quoted string split across lines
+			dev_err(info->dev, "failed: irq request (IRQ: %d,"
+				" error :%d)\n", muic_irq->irq, ret);

- warning message about coding style.

	drivers/extcon/extcon-sm5502.c:398 sm5502_muic_cable_handler()
		warn: we tested 'attached' before and it was 'false'

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>