ARM: uniphier: remove unused header file

This has been unused since commit f4e190e3 ("ARM: uniphier:
enable SPL_OF_CONTROL").
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

arch/arm/mach-uniphier/include/mach/platdevice.h

-/*
- * Copyright (C) 2014 Panasonic Corporation
- *   Author: Masahiro Yamada <yamada.m@jp.panasonic.com>
- *
- * SPDX-License-Identifier:	GPL-2.0+
- */
-
-#ifndef ARCH_PLATDEVICE_H
-#define ARCH_PLATDEVICE_H
-
-#include <dm/platdata.h>
-#include <dm/platform_data/serial-uniphier.h>
-
-#define SERIAL_DEVICE(n, ba, clk)					\
-static struct uniphier_serial_platform_data serial_device##n = {	\
-	.base = ba,							\
-	.uartclk = clk							\
-};									\
-U_BOOT_DEVICE(serial##n) = {						\
-	.name = DRIVER_NAME,						\
-	.platdata = &serial_device##n					\
-};
-
-#endif /* ARCH_PLATDEVICE_H */