serial: imx: fix comment about UCR2_SRST and its handling for shadowing

Initially when register shadowing was introduced (commit 3a0ab62f
("serial: imx: implement shadow registers for UCRx and UFCR")) the logic
to handle UCR2_SRST was wrong but documented consistently. Later the
handling was fixed, but the comment was not. This change makes up leeway
for the latter.

Fixes: 0aa821d8 ("serial: imx: fix cached UCR2 read on software reset")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -314,7 +314,8 @@ static u32 imx_uart_readl(struct imx_port *sport, u32 offset)
 		/*
 		 * UCR2_SRST is the only bit in the cached registers that might
 		 * differ from the value that was last written. As it only
-		 * clears after being set, reread conditionally.
+		 * automatically becomes one after being cleared, reread
+		 * conditionally.
 		 */
 		if (!(sport->ucr2 & UCR2_SRST))
 			sport->ucr2 = readl(sport->port.membase + offset);