tty/serial: atmel: use offset_in_page() macro

Use offset_in_page() macro instead of open-coding.

Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Acked-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/atmel_serial.c

@@ -46,6 +46,7 @@
 #include <linux/err.h>
 #include <linux/irq.h>
 #include <linux/suspend.h>
+#include <linux/mm.h>
 
 #include <asm/io.h>
 #include <asm/ioctls.h>
@@ -959,7 +960,7 @@ static int atmel_prepare_tx_dma(struct uart_port *port)
 	sg_set_page(&atmel_port->sg_tx,
 			virt_to_page(port->state->xmit.buf),
 			UART_XMIT_SIZE,
-			(unsigned long)port->state->xmit.buf & ~PAGE_MASK);
+			offset_in_page(port->state->xmit.buf));
 	nent = dma_map_sg(port->dev,
 				&atmel_port->sg_tx,
 				1,
@@ -1141,7 +1142,7 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
 	sg_set_page(&atmel_port->sg_rx,
 		    virt_to_page(ring->buf),
 		    sizeof(struct atmel_uart_char) * ATMEL_SERIAL_RINGSIZE,
-		    (unsigned long)ring->buf & ~PAGE_MASK);
+		    offset_in_page(ring->buf));
 	nent = dma_map_sg(port->dev,
 			  &atmel_port->sg_rx,
 			  1,