serial: imx: disable console clocks on unregister

During console setup imx_uart_console_setup() enables clocks, but they
are never disabled when the console is unregistered, this leads to
clk_prepare_enable() being called multiple times without a matching
clk_disable_unprepare() in case of console unregister.

Ensure that clock enable/disable are balanced adding
clk_disable_unprepare() in the console exit callback.

Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Link: https://lore.kernel.org/r/20211020192643.476895-3-francesco.dolcini@toradex.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -2124,12 +2124,24 @@ error_console:
 	return retval;
 }
 
+static int
+imx_uart_console_exit(struct console *co)
+{
+	struct imx_port *sport = imx_uart_ports[co->index];
+
+	clk_disable_unprepare(sport->clk_per);
+	clk_disable_unprepare(sport->clk_ipg);
+
+	return 0;
+}
+
 static struct uart_driver imx_uart_uart_driver;
 static struct console imx_uart_console = {
 	.name		= DEV_NAME,
 	.write		= imx_uart_console_write,
 	.device		= uart_console_device,
 	.setup		= imx_uart_console_setup,
+	.exit		= imx_uart_console_exit,
 	.flags		= CON_PRINTBUFFER,
 	.index		= -1,
 	.data		= &imx_uart_uart_driver,