gpio: omap: avoid clang warning

clang warns about a tentative array definition in the gpio-omap driver:

drivers/gpio/gpio-omap.c:1282:34: error: tentative array definition assumed to have one element [-Werror]
static const struct of_device_id omap_gpio_match[];

It's best to just reorder the entire file to avoid forward declarations,
which lets us use the regular declaration. To do this, the unnecessary
CONFIG_OF check must also be removed.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>