gpiolib: remove empty asm/gpio.h files

The arm and sh versions of this file are identical to the generic
versions and can just be removed.

The drivers that actually use the sh3 specific version also include
cpu/gpio.h directly, with the exception of magicpanelr2, which is
easily fixed. This leaves coldfire as the only gpio driver
that needs something custom for gpiolib.

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>