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>