serial: 8250_dw: Introduce IO accessors to extended registers

There are several extended (in comparison to the traditional 16550)
registers are present in Synopsys DesignWare UART. All of them
are 32-bit ones.

Introduce helpers to simplify access to them and convert existing users.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_dw.c

@@ -67,6 +67,21 @@ struct dw8250_data {
 	unsigned int		uart_16550_compatible:1;
 };
 
+static inline u32 dw8250_readl_ext(struct uart_port *p, int offset)
+{
+	if (p->iotype == UPIO_MEM32BE)
+		return ioread32be(p->membase + offset);
+	return readl(p->membase + offset);
+}
+
+static inline void dw8250_writel_ext(struct uart_port *p, int offset, u32 reg)
+{
+	if (p->iotype == UPIO_MEM32BE)
+		iowrite32be(reg, p->membase + offset);
+	else
+		writel(reg, p->membase + offset);
+}
+
 static inline int dw8250_modify_msr(struct uart_port *p, int offset, int value)
 {
 	struct dw8250_data *d = p->private_data;
@@ -404,20 +419,14 @@ static void dw8250_setup_port(struct uart_port *p)
 	 * If the Component Version Register returns zero, we know that
 	 * ADDITIONAL_FEATURES are not enabled. No need to go any further.
 	 */
-	if (p->iotype == UPIO_MEM32BE)
-		reg = ioread32be(p->membase + DW_UART_UCV);
-	else
-		reg = readl(p->membase + DW_UART_UCV);
+	reg = dw8250_readl_ext(p, DW_UART_UCV);
 	if (!reg)
 		return;
 
 	dev_dbg(p->dev, "Designware UART version %c.%c%c\n",
 		(reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff);
 
-	if (p->iotype == UPIO_MEM32BE)
-		reg = ioread32be(p->membase + DW_UART_CPR);
-	else
-		reg = readl(p->membase + DW_UART_CPR);
+	reg = dw8250_readl_ext(p, DW_UART_CPR);
 	if (!reg)
 		return;