Serial: ns16550: Add support for CONFIG_SYS_NS16550_IER macro

On some processors this ier register configuration is different
for ex. Marvell Armada100

This patch introduce CONFIG_SYS_NS16550_IER macro support to
unconditionally initialize this register.

Signed-off-by: Prafulla Wadaskar <prafulla@marvell.com>

drivers/serial/ns16550.c

@@ -24,9 +24,13 @@
 #define serial_in(y) 	readb(y)
 #endif
 
+#ifndef CONFIG_SYS_NS16550_IER
+#define CONFIG_SYS_NS16550_IER  0x00
+#endif /* CONFIG_SYS_NS16550_IER */
+
 void NS16550_init (NS16550_t com_port, int baud_divisor)
 {
-	serial_out(0x00, &com_port->ier);
+	serial_out(CONFIG_SYS_NS16550_IER, &com_port->ier);
 #if defined(CONFIG_OMAP) && !defined(CONFIG_OMAP3_ZOOM2)
 	serial_out(0x7, &com_port->mdr1);	/* mode select reset TL16C750*/
 #endif
@@ -52,7 +56,7 @@ void NS16550_init (NS16550_t com_port, int baud_divisor)
 #ifndef CONFIG_NS16550_MIN_FUNCTIONS
 void NS16550_reinit (NS16550_t com_port, int baud_divisor)
 {
-	serial_out(0x00, &com_port->ier);
+	serial_out(CONFIG_SYS_NS16550_IER, &com_port->ier);
 	serial_out(UART_LCR_BKSE | UART_LCRVAL, &com_port->lcr);
 	serial_out(0, &com_port->dll);
 	serial_out(0, &com_port->dlm);