MIPS: JZ4740: Forward declare struct uart_port in header.

As suggested by Geert Uytterhoeven <geert@linux-m68k.org>.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Cc: Antony Pavlov <antonynpavlov@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Lars-Peter Clausen <lars@metafoo.de>

arch/mips/jz4740/serial.h

@@ -16,6 +16,8 @@
 #ifndef __MIPS_JZ4740_SERIAL_H__
 #define __MIPS_JZ4740_SERIAL_H__
 
+struct uart_port;
+
 void jz4740_serial_out(struct uart_port *p, int offset, int value);
 
 #endif