ARM: UniPhier: remove dummy gpio.h

This dummy header was introduced by commit 630bf80ebb (ARM:
UniPhier: add dummy gpio.h to enable CONFIG_OF_CONTROL).

Thanks to commit a08d643dbd (dm: Drop gpio.h header from
fdtdec.c), such an ugly workaround is no longer needed.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>

arch/arm/include/asm/arch-uniphier/gpio.h

@@ -1,6 +0,0 @@
-/*
- * Dummy header file to enable CONFIG_OF_CONTROL.
- * If CONFIG_OF_CONTROL is enabled, lib/fdtdec.c is compiled.
- * It includes <asm/arch/gpio.h> via <asm/gpio.h>, so those SoCs that enable
- * OF_CONTROL must have arch/gpio.h even if GPIO is not supported.
- */