gpio: clps711x: delete local <mach/gpio.h> header

This header file is unused and we shall not add new headers
to the <mach/*> namespace. The macro may be reintroduced when
there is a user for it.

Cc: Alexander Shiyan <shc_work@mail.ru>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>